List of figures

List of tables

 3: Comparative table of phenotypic and genotypic differential characteristics. .... Table 4:

Introduction Chapter I: Introduction I) Introduction of deep-sea hydrothermal vents

For a long time, no one suspected that life could thrive in the abyssal depths of the oceans. The year 1977 was a turning point in the field of biology: a dive of the submersible Alvin in Galápagos rift at 2500 m below sea level has shed light on organisms living near deep-sea thermal hot spring [START_REF] Corliss | Oases of Life in the Cold Abyss[END_REF][START_REF] Corliss | Submarine Thermal Sprirngs on the Galápagos Rift[END_REF]. These hot springs are also known as deep-sea hydrothermal vent. Light can only diffuse in the upper layers of oceans, so these ecosystems are based on chemosynthetic microorganisms, which turn inorganic carbon into organic molecules [START_REF] Corliss | Submarine Thermal Sprirngs on the Galápagos Rift[END_REF] using energy from inorganic molecules instead of light.

1) Generalities about deep-sea hydrothermal vents

Since their discovery in 1977, deep-sea hydrothermal vents (DSHV) are subject to intense scientific investigations as their ecology and functioning is in sharp contrast with surface ecosystems. They are present all around oceans in active volcanic areas (Figure 1), and they are distributed from sea level to 4964 m. The Beebe vent field at the Cayman rise is the actual deepest known vent field [START_REF] Connelly | Hydrothermal vent fields and chemosynthetic biota on the world s deepest seafloor spreading centre[END_REF]. In these active areas, the oceanic crust is fissured due to the thermal activities and this leads to increase in its permeability. Cold seawater can percolate through these cracks, the heat source beneath the ocean crust. On its way, water reacts with warm rocks and washes them out. The resulting fluid is hot (up to 400°C) and chemically reduced. It then rises through the ocean crust. When the hydrothermal fluid mixes with cold seawater, 2-3°C, minerals carried by the fluid precipitate (Figure 2). This phenomenon forms a growing vertical structure called hydrothermal chimney or Black smoker [START_REF] Edmond | Chemistry of hot springs on the East Pacific Rise and their effluent dispersal[END_REF]. Each hydrothermal vent field is different in terms of chemical composition. This is due to multiple parameters: dilution rate of fluid in seawater, seabed mineral composition, and the geophysical context (pressure and temperature used to influence chemical reactions) (Wetzel and Shock, 2000). When seawater penetrates the ocean crust, it starts to loose chemical elements such as dissolved 02, SO4 2-, PO4 2-, NO3 -, Mg 2+ , and on the other hand, leaches metallic compounds (Zn 2+ , Mn 2+ , Fe 2+ , Cu 2+ ) and dissolved gases like H2, H2S, CH4, CO and CO2 (Kelley et al., 2002;Von Damm, 1995). At this stage, it is no longer seawater but hot and anoxic hydrothermal fluid. Mainly the rocks of seabed, basalts or peridiotites, influence its composition (Wetzel and Shock, 2000). This leads into two categories of vent fields: on the one hand ultramafic vent systems with a peridotite basement, and on the other hand, basalt-hosted system with predominance of basalts in seabed. In general, hydrothermal fluid in ultramafic context is characterized by high dihydrogen and methane concentrations, whereas fluid from basalt-hosted hydrothermal systems is enriched in dihydrogen sulfide and is deprived of dihydrogen and methane (McCollom, 2007;Wetzel and Shock, 2000).

Hydrothermal vents are located on average at 2000 m water depth, well below the light penetration limit of the ocean surface. In addition, it is estimated that only 1% of the organic material produced in the upper layers of the ocean can sink to the seabed (Jannasch and Taylor, 1984). Consequently, chemosynthetic lithotrophic Bacteria and Archaea that can produce complex organic molecules from the fixation of CO2 are at the basis of trophic web. In abysses, there is a strong hydrostatic pressure. It increases of 0.1 MPa every 10 m of water column, either the value of the atmospheric at the sea level. Further, the hydrothermal fluid can be very hot, 350-400°C, and acid, pH 2-4 (Martin et al., 2008;Von Damm, 1995), while surrounding water is cold, 2-3°C and nearly neutral. When hydrothermal fluid and water mix together, it creates intense physical-chemical gradients. All these parameters mean that DSHV are qualified as an extreme environment.

2) Deep-sea hydrothermal vent ecology

Hydrothermal vents are often compared to oases of life within abyssal deserts. They indeed harbor a striking number of metazoans: shrimps (Rimicaris exoculata), crabs (Bythograea thermydron), mollusks (Bathymodiolus thermophilus), giant tube worm (Alvinella pompejana), etc. [START_REF] Lutz | Ecology of deep-sea hydrothermal vent communities: A review[END_REF]. Also, microbial diversity is studied since the discovery of DSHV. The first way to do this is classical in microbiology: isolating microorganisms in pure culture and studying their phenotypes. But as many bacterial and archaeal lineages are still eluding cultivation, additional approaches based on direct environmental DNA sequencing are often used to explore taxonomic and functional diversity. Since the advent of high throughput sequencing technologies, the number of candidate microbial species/genera associated to DSVH is constantly increasing. Of course, viruses and Eukarya should not be forgotten, but this work is only focused on microorganisms belonging to an archaeal order.

Both Archaea and Bacteria are found in different ecological niches: in the hydrothermal plume, on the walls of chimney, in sediments and associated with fauna.

Concerning Archaea, most of the lineages belong to the Euryarchaeota phylum. It includes Thermococcales, Methanococcales, Methanopyrales, Archaeoglobales, Halobacteriales, and the Deep-sea Hydrothermal Vent Euryarchaeota group 2 (DHVE2) (Flores et al., 2012;Fortunato and Huber, 2016;Nakagawa and Takai, 2008;[START_REF] Dalmasso | Thermococcus piezophilus sp. nov., a novel hyperthermophilic and piezophilic archaeon with a broad pressure range for growth, isolated from a deepest hydrothermal vent at the Mid-Cayman Rise[END_REF][START_REF] Roussel | Comparison of microbial communities associated with three Atlantic ultramafic hydrothermal systems[END_REF]Takai and Nakamura, 2011). Some other lineages belong to the TACK (Thaumarchaeota, Aigarchaeota, Crenarchaeota, and Korarcheota) superphylum (Guy and Ettema, 2011). These are mainly Desulfurococcales and Nitrosupumilales (Fortunato and Huber, 2016). Phylogenetic placement of some newly discovered archaeal clades is still controversial, like the Lokiarchaeota phylum [START_REF] Da Cunha | Lokiarchaea are close relatives of Euryarchaeota, not bridging the gap between prokaryotes and eukaryotes[END_REF]Spang et al., 2015). Spang and collaborators identified these new organism from metagenomics data, collected at Loki s Castle vent site Arctic Ocean).

Bacterial communities are found mostly in less warm niches of the hydrothermal vents.

Mainly, Proteobacteria (by abundance: Epsilon-, Gamma-, Alpha-and Delta-) represent the vast majority of bacterial lineages in DSHV. There are also Aquificales, Bacteroidetes, Firmicutes and Thermotogales (Figure 3) (Flores et al., 2011;Huber et al., 2006;Nakagawa and Takai, 2008;Orcutt et al., 2011;[START_REF] Dalmasso | Thermococcus piezophilus sp. nov., a novel hyperthermophilic and piezophilic archaeon with a broad pressure range for growth, isolated from a deepest hydrothermal vent at the Mid-Cayman Rise[END_REF]Teske et al., 2002). The deep-sea shrimp, Rimicaris exoculata is known to harbor a complex symbiosis with microorganisms. The community associated with R. exoculata is dominated by Epsilonproteobacteria [START_REF] Guri | Acquisition of epibiotic bacteria along the life cycle of the hydrothermal average nucleotide identity[END_REF].

3) Extremophiles

Extremophile, from the Latin extremus and the Greek philiā , means literally love the extreme . The word Extremophile was proposed in the to facilitate the communication about organisms able to populate environments hostile to mesophiles, or organisms which grow only in intermediate environments [START_REF] Macelroy | Some comments on the evolution of extremophiles[END_REF]. To date, an accepted definition of extremophile is an organism that thrives under chemical or physical extreme conditions, such as high or low pH or temperature, high salinity or pressure (Horikoshi and Bull, 2011;[START_REF] Madigan | Brock biology of microorganisms[END_REF]. This definition is anthropocentric thought. What seems extreme for a human, for example temperature above 80°C, is absolutely normal and contribute to the proper development of hyperthermophilic Archaea. Although the word extremophile often refers to unicellular microorganisms members of Archaea or Bacteria, some fungi can live in extreme acid environments. And other Eukarya like the well-known micro-animal Tardigrade that can bear with multiple extreme conditions [START_REF] Rothschild | Life in extreme environments[END_REF][START_REF] Seki | Preserving tardigrades under pressure[END_REF]. Even though 14 different extremophilies are listed in the Extremophile Handbook (Horikoshi and Bull, 2011), it refers mostly to the following physicochemical parameters: temperature (psychrophile and (hyper-)thermophile), pH (acidophile and alkaliphile), salinity (halophile) and pressure (piezophile).

Thermophile means every organism that needs a sufficiently hot environment to thrive.

The thermophilic feature is delimited by the value of 40°C as the lower threshold for an organism to develop. This group of organisms is split into two categories: a thermophile organism has an optimum growth temperature upper or equal to 45°C, and a hyperthermophile has an optimum growth temperature above 80°C (Figure 4) [START_REF] Madigan | Brock biology of microorganisms[END_REF]. Within thermophiles, are present some Eukarya, among which fungi have the upper temperature limit. This value is between 60°C and 65°C [START_REF] Madigan | Brock biology of microorganisms[END_REF]Maheshwari et al., 2000;Tansey and Brock, 1972). Beyond this limit of 65°C, only Bacteria and Archaea can live. If we increase the temperature to 80°C and above, almost all microorganisms able to grow are anaerobic Archaea (Stetter, 2006). The story of thermophilic microorganisms started in 1965 when a microbiologist, Thomas Brock, discovered in thermal springs of Yellowstone national park and California (USA), a bacterium that can optimally grow at 70°C [START_REF] Brock | Thermus aquaticus gen. n. and sp. n., a Nonsporulating Extreme Thermophile[END_REF].

Consequences of this discovery are multiple: it opened a new field of research on the discovery of new organisms able to grow at high temperature; study the physiology and ecology of such organisms; find new molecule of biotechnological interest. As an example of this last topic, the DNA polymerase (an enzyme that catalyze the synthesis of DNA during the replication step) from Thermus aquaticus, the bacterium isolated by T.

Brock, has allowed to develop a technic widely use in molecular biology: the polymerase chain reaction (PCR) (Chien et al., 1976;Guyer and Koshland, 1989;[START_REF] Saiki | Enzymatic amplification of beta-globin genomic sequences and restriction site analysis for diagnosis of sickle cell anemia[END_REF].

II) The third domain of life: Archaea

1) Generalities

This work has focused on Thermococcus, a hyperthermophilic Archaea found primarily in deep-sea hydrothermal environments. Archaea is the 3 rd domain of life. It is by working on the composition of ribosomal RNA sequences that Woese and Fox emitted the hypothesis of a third domain of life [START_REF] Woese | Phylogenetic structure of the prokaryotic domain: The primary kingdoms[END_REF]. Indeed, they found that life is split into 3 domains: the first contains all organisms that are affiliated to Bacteria.

The second gather all eukaryotic organisms together (further Eukarya). And the third is composed of only methanogenic bacteria [START_REF] Woese | Phylogenetic structure of the prokaryotic domain: The primary kingdoms[END_REF]. For the authors, this new group is more than a subdivision of the Bacteria kingdom, like Gram-positive and Gram-negative . So they proposed a name for this group, the Archaebacteria. The Greek root of Archaea (άρχάίος) means ancient. This name refers to the methanogenic phenotype of these organisms that is suspected to have appeared earcly on during life development on the Earth [START_REF] Woese | Phylogenetic structure of the prokaryotic domain: The primary kingdoms[END_REF]. Few years later, within this new group and based on 16S rRNA genes, a study proposed to divide Archaeabacteria into two phyla. The first comprised methanogens and halophiles, while the second is composed of Sulfolobus, a thermoacidophile (Fox et al., 1980). These two groups have subsequently been confirmed, and named Euryarchaeota and Crenarchaeota respectively. Ten years later, Woese and collaborators proposed the concept of domain: a taxonomic rank above the kingdom, because their result did not match with the Whittaker s taxonomy based on the five kingdoms Animalia, Plantae, Fungi, Protista and Monera) and the dichotomy Eukaryote-Prokaryote [START_REF] Whittaker | Protist classification and the kingdoms of organisms[END_REF][START_REF] Woese | Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya[END_REF]. These 3 domains are: Archaea, Bacteria and Eukarya (previously named Eukaryota). Woese and colleagues proposed to keep the actual kingdom ranks, and create two new kingdoms for the Archaea domain: the Euryarchaeota and the

Crenarchaeota.

Phylogeny of Archaea is a broadly discussed topic within the scientific community.

Metagenomics and single-cell genomics, two major technics that allow the discovery of new lineages in a culture-independent way, is now widely used to populate the archaeal tree. Even with this massive amount of data, the Archaea domain root and the structure of archaeal phyla/superphyla/kingdom is still under debate [START_REF] Da Cunha | Lokiarchaea are close relatives of Euryarchaeota, not bridging the gap between prokaryotes and eukaryotes[END_REF]Hug et al., 2016;Petitjean et al., 2015;Raymann et al., 2015;[START_REF] Rinke | Insights into the phylogeny and coding potential of microbial dark matter[END_REF][START_REF] Williams | Integrative modeling of gene and genome evolution roots the archaeal tree of life[END_REF][START_REF] Zaremba-Niedzwiedzka | Asgard archaea illuminate the origin of eukaryotic cellular complexity[END_REF], and even the existence of an archaeal domain [START_REF] Cossu | Comparative genomics reveals conserved positioning of essential genomic clusters in highly rearranged Thermococcales chromosomes[END_REF]Spang et al., 2015).

According to recent phylogenies, the Archaea domain is divided in 4. The first part is the phylum Euryarchaeota, which include, among other orders, Thermococcales. The second is the superphylum TACK (Guy and Ettema, 2011), witch includes the four initials phyla:

Thaumarchaeota, Aigarchaeota, Crenarchaeota and Korarchaeota; and the three new phyla: Bathyarchaeota [START_REF] Meng | Genetic and functional properties of uncultivated MCG archaea assessed by metagenome and gene expression analyses[END_REF], Vestraetearchaeota (Vanwonterghem et al., 2016) and Geoarchaeota (Kozubal et al., 2013). The third is the superphylum Asgard, where the phyla Heimdallarchaeota [START_REF] Zaremba-Niedzwiedzka | Asgard archaea illuminate the origin of eukaryotic cellular complexity[END_REF], Thorarchaeota [START_REF] Seitz | Genomic reconstruction of a novel, deeply branched sediment archaeal phylum with pathways for acetogenesis and sulfur reduction[END_REF], Odinarchaeota [START_REF] Zaremba-Niedzwiedzka | Asgard archaea illuminate the origin of eukaryotic cellular complexity[END_REF] and Lokiarchaeota (Spang et al., 2015) are present. The last major cluster is the superphylum DPANN (Castelle et al., 2015;[START_REF] Rinke | Insights into the phylogeny and coding potential of microbial dark matter[END_REF], which includes the following phyla: Woesarchaeota, Pacearchaeota, Mamarchaeota, Pavarchaeota, Nanoarchaeota, Nanohaloarchaeota, Aenigmarchaeota, Micrarchaeota, Diapherotrites and Altiarchaeales (Figure 5).

In contrast to TACK and Euryarchaeota, the two superphyla DPANN and Asgard are only composed of genomes extracted from metagenomes, and none of them are cultivated (Adam et al., 2017, Castelle andBanfield, 2018).

All works of this thesis will focus on hyperthermophilic and anaerobic microorganisms that belong to the Thermococcales order.

2) The order Thermococcales

Thermococcales is an archaeal order that belongs to the domain of Archaea, phyla of Euryarchaeota and class of Thermococci. This order is composed of three genera:

Thermococcus (Zillig et al., 1983), Pyrococcus (Fiala and Stetter, 1986) and Palaeococcus (Takai et al., 2000). Members of Thermococcales are cocci of about 1 µm in diameter.

They are strict anaerobes, with some exceptions (Amend et al., 2003;Thorgersen et al., 2012), hyperthermophiles and heterotrophs. Additionally, few members of Thermococcus have the ability to grow lithotrophically by anaerobic oxidation of CO (Lee et al., 2008;Sokolova et al., 2004). They can use a broad range of molecules as carbon source (proteins, peptides, carbohydrates) by fermentation. For certain isolates, S 0 stimulates their growth, while others require S 0 to grow indicating a mixed fermentative / anaerobic respiration energy conservation strategy. Thermococcales are often isolated from both deep-sea and shallow hydrothermal environments (Pyrococcus is only found in deep-sea). There is however exceptions, for example Thermococcus sibiricus, which was isolated from a siberian high-temperature oil reservoir (Miroshnichenko et al., 2001). Their optimal growth temperature range between 75 and 100°C (Kobayashi, 2015;Stetter and Huber, 2015;Takai, 2015;Zillig and Reysenbach, 2015). To date, 45 species of Thermococcales are characterized (Table 1). In molecular studies, Thermococcales are always found in deep-sea hydrothermal ecosystems, all around the globe. From these studies, Thermococcales form a minor part of the microbial community at vent sites.

However, they are relatively easy to isolate, as evidenced by the large number of isolates available in Taxonomy database NCB) and in culture collections.

Unsurprisingly, Thermococcales thus constitute the order with the largest number of isolates in the LM2E culture collection (UBOCC), with around 300 isolates available.

From the biotechnology point of view, the most striking application is the DNA polymerase of Pyrococcus furiosus. This enzyme is known as Pfu polymerase . )t is widely used in PCR thanks to its high fidelity compared to the traditional Taq polymerase. In addition of its polymerase activity, Pfu polymerase has aexonuclease activity that enhances its fidelity [START_REF] Lundberg | High-fidelity amplification using a thermostable DNA polymerase isolated from Pyrococcus furiosus[END_REF]. This enzyme was patented for the first time in under patents US and US .

On the genomics side, 38 completes genomes are currently available on NCBI (Genomes database). They distribute as follow: 1 Palaeococcus, 10 Pyrococcus and 27

Thermococcus (Table 2). [40.3 -44.6] (Table 2). Although these microorganisms are hyperthermophile, their G+C content is not as high as expected.

Indeed, in vitro, the temperature of DNA denaturation is function of the G+C content of the sequence. But in vivo, DNA stability may be enhanced by ions, proteins or metabolites (Jaenicke and Sterner, 2006). No correlation has been established between the optimal growth temperature of a microorganism and the G+C content of its DNA molecule [START_REF] Galtier | Relationships Between Genomic G+C Content, RNA Secondary Structures, and Optimal Growth Temperature in Prokaryotes[END_REF]. Nevertheless, according to Galtier and Lobry, this correlation exists between sequences of RNA (ribosomal and transfer) and the optimal growth temperature. Thermococcales harbor one chromosome, however some members of Pyrococcus and Thermococcus possess also mobile genetic elements. They are split into two classes: viruses and plasmids. As example of viruses, we can cite the two currently characterized ones: Pyrococcus abyssi virus 1 [START_REF] Geslin | PAV1, the First Virus-Like Particle Isolated from a Hyperthermophilic Euryarchaeote, Pyrococcus abyssi[END_REF] and

Thermococcus prieurii virus 1 (Gorlas et al., 2012). Concerning plasmids, nearly 20 are described within the genera Thermococcus and Pyrococcus. The first one was identified in 1992, from a Pyrococcus abyssi isolate [START_REF] Erauso | Sequence of plasmid pGT5 from the archaeon Pyrococcus abyssi: evidence for rollingcircle replication in a hyperthermophile[END_REF]. These small molecules are known as vector for exchanging genetic information between cells. Thus this can increase genetic diversity within their hosts. Thermococcus nautili harbors a remarkable plasmid, pTN3, which encode an integrase. This enzyme drives large-scale genomic inversions in few generations. According to Cossu and colleagues [START_REF] Cossu | Flipping chromosomes in deep-sea archaea[END_REF], this shuffling mechanism could occur in case of rapid environmental changes, by

providing alternate patterns of gene expression. Thermococcus waiotapuensis (González et al., 1999) Thermococcus zilligii [START_REF] Ronimus | The phylogenetic position of the Thermococcus isolate AN1 based on 16S rRNA gene sequence analysis: a proposal that AN1 represents a new species, Thermococcus zilligii sp[END_REF] Pyrococcus chitonophagus (Huber et al., 1995;[START_REF] Lepage | Molecular diversity of new Thermococcales isolates from a single area of hydrothermal deep-sea vents as revealed by randomly amplified polymorphic DNA fingerprinting and 16S rRNA gene sequence analysis[END_REF] Pyrococcus abyssi [START_REF] Erauso | Pyrococcus abyssi sp. nov., a new hyperthermophilic archaeon isolated from a deep-sea hydrothermal vent[END_REF]

Thermococcus

Pyrococcus

III) Ordering microbial diversity in cohesive units

1) The necessity to classify microorganisms a) Historical motivations

Classification is an a priori condition for rational thought, so we could not perform any reasoning without them. This behavior can be applied to living beings and is motivated by the fact that our environment is so diverse that it is easier to apprehend a summarized and organized version of its entirety. But this brings approximations because we often elude the uniqueness of all individual components of such units.

Ordering things into ontological units is a way to reach this goal. In the 18 th century, a scientist undertook to classify living things. Carl von Linné, a Swedish botanist and zoologist, undertook to classify the living beings (Animals and Plants). In his main book, Systema Naturae first published in 1735, he classified Animals into 4 400 species and Plants into 7 700 species. As in our modern classification system, Carl von Linné uses nested boxes to order all these living beings. After many attempts to classify living beings, the last accepted classification system is the one published by Woese and colleagues in 1990, with Bacteria, Archaea and Eukarya as the mains upper level units.

b) Classification of living beings

The classification of organisms (living or fossil) followed progresses of science. First, classifications were built based on the morphological features of compared species.

Since the advent of DNA sequencing, classification of organisms is based on molecular markers, such as SSU rRNA. Modern classification is generally based on 9 ranks (Figure 6). Living organisms are called by a binomial name (inherited from Linnaeus classification) that is: the genus and species names. The last rank, species, is the most discussed among microbiologists. For Eukarya, more precisely Animals and Plants, a common definition of the species is a group of organisms with the potential to interbreed and produce viable and fertile offspring (Cohan, 2002;Mayr, 1942). This biological species concept has the major disadvantage of being inaplicable to organisms without sexual reproduction such as Bacteria and Archaea.

Owing to the huge number of microbial cells present on Earth, microbiologists had to find a way to classify them, to make this diversity more apprehensible. It appeared necessary to create units. This can be done by operational criterions, like in the current microbial species definition. In metagenomics, and more generally in microbial community studies, the notion of Operational Taxonomic Unit (OTU) is widely used. It defines groups of sequences, and therefore microorganisms, that share enough similarity. The second way is the Relative Binding Ratio (RBR), which is expressed in percentage of similarity. It is this value that is most often determined. Briefly, it is the relative proportion of DNA heteroduplex in comparison to the DNA homoduplex. The latter is supposed to be 100% (Rosselló-Mora and Amann, 2001). To determine whether two strains belong to the same species, it is recommended to have a DNA-DNA relatedness greater than % and/or a ΔTm lower than 5°C (Wayne et al., 1987). Currently, DDH has been largely replaced by an in silico version. For instance, the genome-to-genome distance calculator (GGDC) hosted on the DSMZ website (Auch et al., 2010a(Auch et al., , 2010b;;[START_REF] Meier-Kolthoff | Taxonomic use of DNA G+C content and DNA-DNA hybridization in the genomic age[END_REF]. This new way to access DDH is better, because it is easier to compare a new isolate with a lot of already sequenced species. And thus, avoid positioning errors in the classification while alleviating wetlab work required for in vivo studies. DDH is a gold standard for delineation of microbial species, but other markers can be used, like the 16S rRNA gene sequence. Firstly, thanks to its ubiquity and the presence of slow and fast evolving regions. Secondly, it is easier and cheaper to obtain the nucleotide sequence of 16S rRNA gene than that of the whole genome. This marker can be a criterion for species delineation, but it should be used in complement of DDH. In general, species having more than 70% DNA relatedness show more than 97% similarity on the 16S rRNA sequence (Stackebrandt and Goebel, 1994) , 2006). Indeed, there is a non-linear relation between 16S rRNA gene sequence similarity and DNA-DNA re-association (Figure 8) (Fox et al., 1992). Authors show that above 70% DNA-DNA similarity, the 16S rRNA is 98.7% or greater, indicating that two strains belong to different species, while the opposite is not true (Figure 8). Above 98.7% 16S rRNA gene sequence similarity between two strains, one cannot conclude if these two strains belong to the same species or not based solely on this marker. DDH is mandatorily to conclude. That is why both values are mandatory for the delineation of new species above 98.7% 16S rRNA gene sequence similarity.

Average Nucleotide Identity

Average Nucleotide Identity (ANI) can be taken into account for defining the microbial species. Even if it is not present in the accepted microbial species definition, this parameter is widely used in characterization of newly isolated strains because it can accurately replace DDH values when genomes of strains are available (Goris et al., 2007;[START_REF] Richter | Shifting the genomic gold standard for the prokaryotic species definition[END_REF]. Indeed, on shared genes between strains, an ANI of 94-95% or above correspond to a 70% or greater DDH (Goris et al., 2007;Konstantinidis and Tiedje, 2005). Slightly different values are found when ANI is based on whole genome sequence: 95-96% [START_REF] Richter | Shifting the genomic gold standard for the prokaryotic species definition[END_REF]. The ANI can be used either on shared genes or on whole genome sequence because it is an in silico analysis (Auch et al., 2010a;[START_REF] Richter | Shifting the genomic gold standard for the prokaryotic species definition[END_REF].

ii) Phenotype

A new species must share resemblances with its closest relatives and have distinct phenotypic features, like for example carbon sources that the strain uses (Stackebrandt et al., 2002). (Thompson et al., 2015).

3) What about a new species definition in the genomic era? a) Currently, definition does not integrate ecology

The current definition does not really encompass the ecology of species, what is the relationship between microorganisms and with their environment. In descriptions of new strain, phenotypes of the isolate are described, but there are no universal rules (Tindall et al., 2010). They can refer to the pathogenicity, the ability to live in water, soil, animal s gut, to play a role in nitrogen fixation, and so on. (ere is the issue: how many phenotypes are required? That is why the definition has to move, or to propose a concept that integrates the ecology of strains, in order to understand global mechanisms underlying differentiation processes.

b) How incorporate ecology and genomic data in a more cohesive model?

Even is these two aspects seems to be strongly linked, the ecology do not clearly appear as a major criterion in the definition. For instance, within E. coli, there are pathogenic strains that infect gut, and other that are able colonize the urinary tract. These two strains have a little less than 42% of shared genes (Welch et al., 2002).

A workflow has been proposed in 2014. It consists in sequencing genomes that occur in the same ecological niche, for instance a single rock sample from a black smoker. Then, we have to cluster genomes into genomic units and make hypothesis about their role in the environment, or what distinguish these units [START_REF] Shapiro | Ordering microbial diversity into Hyperthermophilic Archaea[END_REF]. These hypotheses can be answered with the predicted functions of genes. For instance, we can find predicted functions that are present only within a genomic cluster, and make an assumption about their role. If it is possible to assess, the information provided by gene flows can help to determine the state of divergence between two or more genomic units.

This framework is called reverse ecology [START_REF] Shapiro | Ordering microbial diversity into Hyperthermophilic Archaea[END_REF], and has the advantage of being without a priori conjectures.

4) Instead of thinking species, think population a) Definition of a population

With the framework proposed above, it is easier to see all closely related genomes as a population. This population is defined as a group of individuals sharing genetic and ecological similarity, and coexisting in a sympatric setting (Hunt et al., 2008;[START_REF] Shapiro | Ordering microbial diversity into Hyperthermophilic Archaea[END_REF]. The sympatric setting refers to microorganisms present in the same place, where barriers to gene flow are low or inexistent. Several mechanisms are involved in the formation of new populations: genetic exchange, for instance homologous recombination (HR), gene frequencies, or mobile genetic elements (Anderson et al., 2017a;[START_REF] Cordero | Ecological Populations of Bacteria Act as Socially Cohesive Units of Antibiotic Production and Resistance[END_REF]Shapiro et al., 2012).

b) Genomic units: how to cluster genomes? i) Sequence similarity A first and easy way to cluster microorganisms is based on the similarity between sequences, as it is the case with DDH, ANI, 16S rRNA or marker gene sequence similarity or average amino acid identity (AAI). Here, as in ecological units, the problem is the use of thresholds, because it is not clear where to put borders. The advantage with these criteria is their convenience, but they group strains/sequences within an operational way (Shapiro et al., 2012). Another way to organize genomes is to build phylogenetic trees, which will represent genotypic clusters [START_REF] Doolittle | Genomics and the bacterial species problem[END_REF]Thompson et al., 2015). To be strongly supported, phylogenetic tree has to be build using concatenation of multiple markers, a set of genes universally distributed (Petitjean et al., 2015), or even all shared genes, i.e. core-genes. Here too, it is not clear where to draw barriers between species.

ii) Genetic units

As all methods based on sequence similarity rely on operational units, other ways have to be used to represent units present in natural ecosystems. Communities of microorganism are not static. They share DNA, they migrate in new niches, they undergo predation by bacteriophages, etc. So clustering genetic units should be done based on migration, mutation rate, recombination and selection (Shapiro et al., 2012).

The first, migration, is difficult to assess because speciation arising from geographic isolation is carried out in an allopatric setting. The last two, recombination and selection, are described as two major elements that drive the speciation in natural sympatric population [START_REF] Shapiro | Ordering microbial diversity into Hyperthermophilic Archaea[END_REF] Choi et al., 2015;Soler et al., 2008), or by virus as in the tree domains of life, or by conjugation when a plasmid can be transferred to another cell (Wagner et al., 2017). Gene flow and point mutation can serve as trigger for separation of population and leads to speciation, unless homologous recombination occurs at a very high rate with population because it homogenizes the genotype of population (Shapiro et al., 2012). Thanks to these two levers, two models have been proposed, the first that can leads to separation or collapsing of population, and the second that is better known under the Ecotype model.

d) Different models exist i) Based on recombination/selection ratio

The recombination/selection ratio depends primarily on the number of homologous recombination, which has the role to homogenize loci or even entire genome, across the population. The second is selection, which favor a particular variant and confer an advantage. This advantage is translated by an increase of its fitness, and thus an increase of its frequency in the population. This can lead to the extinction of the other variants. The balance between these two elements defines two speciation models.

The first is the stable ecotype model , when rate of recombination is well below the rate of selection (Table 4). In this model, an adaptive mutant arises in a population, this can lead to ecological separation in a new niche, or this mutation can purge the diversity by outcompeting its close neighbors in a periodic selection event. The diversity is purged only in the ecotype where the mutant arises, the other ecotypes are not affected by this selection event because they are in independent niches [START_REF] Cohan | A Systematics for Discovering the Fundamental Units of Bacterial Diversity[END_REF].

This model states that adaptive and neutral loci in the genome cannot be unlinked through observed rates of homologous recombination because it is too low. So it is a genome-wide selective sweep (Figure 9). The second case is where homologous recombination is greater than the selection rate.

Here, barriers to gene flow are low or non-existent, and the rate of homologous recombination is high enough to avoid incorporation of polymorphism due to genetic drift. This polishing of polymorphism is only valid for adaptive loci. But there could be a mutation in a part of the population that brings it the ability to switch in a new niche (Table 4). This adaptive variant will spread in the new population by gene-sweep, i.e. homologous recombination. At this time, if gene flow decreases, it will result in two distinct populations as in figure 10, else the newly divergent groups could merge back together and purge polymorphisms in adaptive loci. It is important to see these speciation models as dynamic processes, if these stages of speciation can be defined, it does not mean that all populations that start at Stage 1 will make it to Stage 5" [START_REF] Shapiro | Ordering microbial diversity into Hyperthermophilic Archaea[END_REF]. Therefore, some lineages can either undergo extinction or new differentiation event at any stage of this process.

5) Examples of natural populations

These models of speciation are based on recent observations of natural populations.

They were made on marine microbe, because it is probably easier to observe large-scale genetic information exchange and new niches colonization in water than in soil owing to the increases mixing and dispersion in the former environment.

a) Vibrio

A study of 20 genomes affiliated to Vibrio cyclitrophicus occurring in the same geographical area and sampled in 2006 and 2009, showed that two populations are present and they are at an early stage of the speciation process (Shapiro et al., 2012).

Indeed, these authors choose the 20 isolates based on a phenotype: free-living or particle-associated (Hunt et al., 2008). Between these genomes, they identified around 28 000 single-nucleotide polymorphisms (SNP), distributed over all genomes. Other SNPs were identified: 725, localized in 11 regions of which 3 include more than 80% of these SNPs. They are called EcoSNPs because they follow the niche separation of the 20 isolates. This ecological specialization is mediated by the size of the particles to which the cells are attached and this may be the result of small variations in genes of critical pathways, like adhesion to surface, virulence factor or biofilm formation (Shapiro et al., 2012). For the authors, these populations are in an early stage of differentiation (Figure 10, sample t1), where neutral loci do not allow us to pinpoint the two emerging populations. If the speciation postulate is verified, homologous recombination will be more likely to occur within than between population, and thus reach the complete separation, i.e. the formation of 2 distinct genotypes.

b) Sulfolobus

Sulfolobus is an archaeal genus belonging to the Creniarcheota phylum. Sulfolobus species are aerobic acidophiles and thermophiles, mostly found terrestrial hot springs [START_REF] Madigan | Brock biology of microorganisms[END_REF]. Within a group a 12 isolates affiliated to Sulfolobus islandicus, which come from the same hot spring, patterns of gene flow (homologous recombination) are in favor with the presence of well separated populations [START_REF] Cadillo-Quiroz | Patterns of gene flow define species of thermophilic Archaea[END_REF]Krause et al., 2014). For the authors, this phenomenon supports an ecological differentiation that can prevent competition between the two populations. In addition, with isolates from the same geographic area, it has been shown that recombination shapes the population structure, according to the speciation framework presented above [START_REF] Whitaker | Recombination Shapes the Natural Population Structure of the Hyperthermophilic Archaeon Sulfolobus islandicus[END_REF].

IV) Objectives of the thesis

In this work, we aim at better understanding the early stages of diversification at the genomic level. During these 3 years of PhD, the common thread was thus the study of closely related Thermococcus isolates genomic diversity, through the lens of comparative genomics studies. Here we expected to observe at least two drivers of diversification: geographical isolation, with which we can assume the presence of migration barriers, and sympatric speciation. For this purpose, a long first part consisted in selecting groups of strains meeting several criteria: number of isolates, geographical origins and group support in marker genes (16S rRNA-ITS) phylogenetic tree.

From these criteria, two groups were selected. They represented 45 genomes, with the first group close to Thermococcus sp. 4557 and T. celericrescens, and the second group is close to T. nautili. Within each group, the aim was to identify functional drivers that group isolates in phylogenetic coherent clusters and thus pinpoint specific genes and functions involvedor resultingin these diversification processes.

At the end, I have started an exploratory study on the dissemination and distribution of Thermococcales cells between deep-sea and shallow hydrothermal vents and also terrestrial hot springs. For this, multiple public metagenomes were mapped on a large dataset of Thermococcales's genomes and we observed the percentage of detection for each genome within each metagenome.

Materials and Methods

Chapter II: Materials and Methods

This chapter gathers all the methods used in this work. It aims to provide an overview of all the steps carried out and to provide details about the techniques used. Specific and more concise sections on materials and methods are available in each subsection of the results.

I) The LM2E culture collection: UBOCC

Strains used in this study are stored in an international culture collection. This collection is established within 2 laboratories: the Laboratory of Microbiology of the Extreme Environments (LM2E, Plouzané, France) for the marine sub-collection, and the Laboratory of Biodiversity and Microbial Ecology (LUBEM, Plouzané, France) for the agri-food sub-collection. In total, around 1 300 isolates are present within this collection.

This study focused on Thermococcales stored in the marine culture collection. Among the 1300 isolates, about 300 strains belonged to this archaeal order and thus constituted an ideal starting material to address the central questions of this study (Appendix 1).

1) Culture of hyperthermophilic and anaerobic isolates

Given that isolates are anaerobic, they were grown in 50 mL serum bottle (Ref:

W012488A, Wheaton ® ) sealed with a rubber stopper. The dioxygen (O2) present in the flask and medium was removed by flushing the flask between 5 to 7 times with dinitrogen (N2). Residual traces of O2 were removed by adding 1% (v/v) of a 5% (w/v) sodium sulfide solution (Na2S. 9H20). The aim of this step was to get a completely reduced medium. The oxidation state of the medium was visualized with a dye, the resazurin. Few drops of a 1% (w/v) solution are sufficient for 1L of medium. When the medium is totally oxidized (before sterilization notably), resazurin is blue. After sterilization, if the media was reduced, resazurin was yellow to colorless. Otherwise resazurin was pink due to oxic conditions. To keep the flask anoxic and sterile during sampling or inoculation, we used sterile needles and syringes. a) Preparation of culture media Thermococcales isolates grow on rich media, like Thermococcus Rich Medium (TRM) or Ravot medium. TRM was composed of (per liter of distilled water): 23 g NaCl; 5 g MgCl2.6H20; 3.46 g Piperazine-N,N′-bis (2-ethanesulfonic acid) (PIPES buffer); 4 g Tryptone; 1 g Yeast extract; 0.7 g KCl; 0.5 g (NH4)2SO4; 0.05 g NaBr; 0.01 g SrCl2.6H20; 0.001 g resazurin. Adjust the pH to 6.8 before sterilization. After sterilization, following solutions were added aseptically: 1mL of 5% (w/v) K2HPO4; 1 mL of 5% (w/v) KH2PO4; 1 mL of 2%(w/v) CaCl2.2H2O; 1 mL of 10 mM Na2O4W.2H20; 1 mL of 25 mM of FeCl3.6H20. To finish, the medium was complemented with 0.5 mL of Balch vitamins solution (Balch et al., 1979;[START_REF] Zeng | Pyrococcus CH1, an obligate piezophilic hyperthermophile: extending the upper pressure-temperature limits for life[END_REF].

Ravot medium was composed of (per liter of distilled water): 1 g NH4Cl; 0.83 g Sodium acetate trihydrate; 0.2 g MgCl2.6H20; 3.45 g Piperazine-N,N′-bis (2-ethanesulfonic acid) (PIPES buffer); 5 g Tryptone; 5 g Yeast extract; 0.1 g KCl; 0.1 g CaCl2.2H20; 20 g NaCl; 0.001 g resazurin. Adjust the pH to 7 before sterilization. After sterilization, multiple solutions were added: 5 mL of 7% (w/v) K2HPO4, 5 mL of 7% (w/v) KH2PO4. To finish, the medium was complemented with 0.5 mL of Balch vitamins solution (Gorlas et al., 2013b).

b) Sterilization steps

Media were sterilized at 121°C for 20 min in a wet atmosphere and under a pressure of 2 bars. For compounds that are thermolabile, like vitamins, they were sterilized by filtration onto 0.22 µm pore-size membranes.

Elemental sulfur (S 0 ) was sterilized in a specific way, the tyndallization. It consisted of a sterilization cycle in wet atmosphere at 100°C during 30 min. This step was repeated 3 times, 1 time per day. c) Culture conditions Uncharacterized putative Thermococcales isolates present in the UBOCC grow at 85°C, except 4 isolates that grow at 80°C. In general, isolates belonging to this order grow rather fast, reaching a stationary phase in less than 24 h. In addition to fermentation, these isolates are known to use S 0 as an electron acceptor during respiration. Hence, tyndallized S 0 was added within each vial, at 2 g.L -1 .

All cultures of microorganisms in this study were performed into 50 mL serum bottle (hereafter named vial). For each vial, 20 mL of complemented medium was added (Figure 11A). Before sealing the flask, S 0 was added under sterile conditions. Then, each vial was flushed with N2. To finish, the reducing agent was added to remove the last traces of O2.

All isolates were stored in the culture collection in 1.8 mL Nunc ® CryoTubes ® at -°C.

To start a culture from a cryovial, the first step was to put isolates back into culture: thaw the sample and transfer 100 to 200 µL aseptically and anaerobically into a vial with 20 mL of reduced medium. Incubate for at least 16 h at the recommended temperature for the isolate. Subcultures were performed by transferring 10% (v/v) of the original culture into a new one, with fresh sterile medium.

d) Cells viability

After 16 to 20 h of incubation, each culture was checked under light microscope (Olympus ® CX41), at x400 and x1000 magnification (Figure 11B). The cell density was appreciated for each culture. In complement to observation, a Cord-Ruwisch test was performed (Figure 11C). The principle is as follow: all these isolates produce hydrogen sulfide (H2S) during their growth. The aim was to precipitate this H2S with a solution of copper sulfate (CuSO4) [START_REF] Cord-Ruwisch | A quick method for the determination of dissolved and precipitated sulfides in cultures of sulfate-reducing bacteria[END_REF]. To do this, 0.1 µL of the culture was added into 1 mL of the solution of acid CuSO4 (HCl 50 mM + CuSO4 5 mM). If H2S was present, a black precipitate of CuS formed immediately. The negative control was performed with 0.1 mL of sterile reduced culture medium.

II) DNA extraction 1) Genomic DNA extraction

DNA of isolates was extracted for two different purposes. The first one was to sequence two taxonomic markers for all Thermococcales isolates of UBOCC. These markers are the ribosomal RNA small subunit or 16S ribosomal RNA (16S rRNA), and the Internal Transcribed Spacer (ITS) that is located between the 16S and the 23S rRNA on the genome. The second purpose was the sequencing of the whole genome of 48 isolates that were selected within the UBOCC.

All DNA extractions were performed with the same phenol-chloroform protocol, based on the hydrophobicity of DNA and the amphiphilic nature of proteins. In order to extract a sufficient quantity of DNA for each sample, 2 vials per isolate were used. They were pooled together in 50 mL Falcon ® tube before the first step of the protocol. The procedure consisted of the following steps:

Centrifuge culture at 8 000 rotations per minute (rpm) for 5 min, at 4°C Discard supernatant under fume hood Homogenize the cell pellet with 1mL of TNE 1X buffer (50 mL Tris-HCl 1 M; 50 mL EDTA 0.5 M pH 8; 10 mL NaCl 5M; q.s.p 500 mL) Transfer this solution in a 2 mL microtube For lysis, add 100 µL of N-Lauroylsarcosine sodium salt (Sarkozyl) 10% 100 µL of Sodium Dodecyl Sulfate (SDS) 10% 50 µL of Proteinase K at 20 mg.mL -1 (ref: V3021, Promega ® ) Incubate at 55°C for 1 h in a water bath. Mix slowly from time to time Add 20 µL of RNase A at 10 mg.mL -1 (Ref: 02101076, MP Biomedicals) Incubate 20 to 30 min at 37°C Add 1 mL of Phenol-Chloroform-Isoamyl alcohol (PCI) (25:24:1) Shake by turning for 45 sec Centrifuge at 14 000 rpm for 15 min at 4°C Recover the aqueous phase (upper phase) If the interface contains a lot of cell fragments, repeat the operation 1 time (1 mL PCI, mix 45 sec, centrifuge, recover supernatant) Add 1 mL of chloroform Shake by turning for 45 sec Centrifuge at 14 000 rpm for 15 min at 4°C Recover the aqueous phase (upper phase) Add . volume of frozen isopropanol -°C Put the tube at -°C for at least h. Possible to leave overnight Centrifuge at 14 000 rpm during 20 min at 4°C Discard the supernatant and resuspend the DNA pellet with 0.5 mL of frozen 75% (v/v) ethanol Centrifuge at 14 000 rpm during 20 min at 4°C Discard the supernatant and dry the DNA pellet at room temperature, tubes returned, or 1 min in SpeedVac DNA , Savant™ at room temperature Resuspend the DNA pellet by adding 50 to 100 µL of low EDTA buffer, for example buffer EB (Ref: 19086, Qiagen)

2) Assessing the quality and quantity of DNA

The quality of DNA after extraction is crucial for the downstream analysis. Various ways are available to check the quality and the quantity. The first one is spectrophotometry.

This technique scans the sample and measures the absorbance at specifics wavelength directly from the sample. Another technique of spectrometry uses a fluorescent dye that inserts between the DNA strands. The second method is the qPCR quantification. The methods used are described below: a) With the spectrophotometer NanoDrop ®

The device used was the NanoDrop ® ND1000 (Figure 12). This first method was rapid and easy to use. The principle was to load 1-2 µL of sample directly on the pedestal and close the sampling arm.

It measured the absorbance of nucleic acids (DNA and RNA), proteins and aromatic organic compounds. Each molecule absorbs at a specific wavelength. Nucleic acids have a strong absorbance at 260 nm. Aromatic amino acids are responsible for the proteins absorbance at a wavelength of 280 nm. And 230 nm is used to evaluate the quantity of organic compounds such as phenol. Moreover, at this wavelength, the peptide bond within proteins absorbs too. The quality evaluation is based on 2 ratios: the A260/A280 ratio and the A260/A230 ratio. The first ratio determines the contamination of a sample by proteins. A DNA sample is considered pure when the ratio is between 1.8 and 2. Below 1.8, the quantity of contaminant can interfere with downstream analysis. The second ratio indicates the degree of contamination of DNA by organic compounds such as phenol. A sample with a ratio between 2 and 2.2 is considered pure.

The NanoDrop ® ND1000 was connected to a computer. Result for each sample was immediately displayed on the screen. Before the first use, the pedestal was loaded with 1-2 µL of sterile MilliQ ® water. Then, a blank was made with 1-2 µL of elution buffer.

The samples could then be loaded one after another. Before each measure, wipe carefully the pedestal with non-abrasive wipes. Result for each sample were given in ng.µL -1 . This value should be taken carefully, because this method quantifies both double-and single-stranded DNA (dsDNA -ssDNA), and also RNA. This device (Figure 12) has to be used in association with NanoDrop ® . The reason is that it can only quantify the targeted molecule (depending on the kit used) within a sample, but do not assess its quality. It is however more accurate because we used a kit designed for dsDNA quantification (Ref. E2670, Promega). This kit contains a fluorescent dye that interleaves within dsDNA, so ssDNA and RNA were not taken into account.

This quantification method depends on a standard curve, prepared with 2 points: 0 ng.µL -1 , and 100 ng.µL -1 , following the manufacturer instructions. The drawback of this method is that the DNA concentration of samples has to fall within this interval. Here, results obtained with the NanoDrop ® are a good indicator of the potential need for a dilution.

The protocol proceeds as follow:

Prepare the buffer TE 1X Dilute the dye with buffer at 1:200 In 500 µL PCR tubes, add 100 µL of TE 1X for each sample and the 2 points of the standard curve Add 1 µL of sample or negative or positive control Add 199 µL of dye diluted in TE 1X and mix thoroughly Incubate 5 min at room temperature, protected from light Calibrate the Quantus ® with controls Measure all samples c) Illumina ® library quantification by qPCR Illumina sequencing technic allows multiplexing samples on a single flowcell, i.e.

sequence more than 1 sequencing library at the same time. To avoid biases, each library should be at the same concentration. The manufacturer recommend to use a qPCR protocol, KAPA Library Quantification Kit Illumina ® platforms (Kapa Biosystems).

According to the manufacturer protocol, each library was diluted at 1:10 000 and 1:20 000 in triplicate. So, 6 wells of the qPCR were dedicated to quantify 1 library. Then Given that, qPCR is very sensitive especially to pipetting errors. That is the reason why all was done in triplicate: negative control, standard curve and each dilution of libraries.

3) Preparation of DNA a) 16S and ITS

For this project, 16S rRNA and ITS markers were sequenced for all isolates using the Sanger technique, this in order to affiliate each isolate within a phylogenetic taxon, i.e.

find the appropriate genus and identify a set of closely related strains suitable for our comparative genomics study. In a second time, 48 isolates were selected for whole genome sequencing. For this part, a multiplexed Illumina sequencing strategy was employed to recover all genomes.

i) PCR protocol 16S rRNA gene sequencing is the gold-standard method to assign a taxonomic position to a microbial isolate owing to the large taxonomic databases available. Here we choose to add the ITS in the sequencing to reconstruct a more robust phylogenetic tree. Indeed, ITS can accumulate mutations at a higher rate than 16S rRNA genes because it is a noncoding fragment.

Three primers were employed for the whole process: A4F (TCC GGT TGA TCC TGC CRG)

with a Tm of 60°C (Reysenbach et al., 2000a), A1492R (GGC TAC CTT GTT ACG ACT T)

with a Tm of 56°C (Teske et al., 2002), and A71R (TCG GYG CCC GAG CCG AGC CAT CC) with a Tm of 62.6°C (Casamayor et al., 2002). The 2 degenerated nucleotides correspond to: A or G R , and C or T Y .

Among these primers, A4F and A71R were used for the PCR. The first primer matches at the beginning of the 16S rRNA gene, in forward way, while the second matches the beginning of the 23S rRNA gene in reverse. Thanks to this primer pair, the whole 16S-ITS sequence could be recovered at the same time. The PCR template employed is presented in figure 13.

Figure 13: PCR template used to amplified the 16S-ITS DNA sequence

The PCR mixture was prepared using the following final concentrations, for 1 reaction: were boiled and then ethidium bromide was added (5 µL for 100 mL). This molecule has the property of being interleaved between the two strands of DNA, and to fluoresce when exposed to ultra-violet (UV) radiation. For each sample, 5 µL of PCR product was loaded within a well. The ladder used was BenchTop 1 kb DNA ladder (Figure 14) (Ref:

GoTaq ® G2
G7541, Promega). The expected size of the amplification fragment was around 1800 bp.

A transilluminator was used to expose the gel and verify amplification results.

III) DNA Sequencing 1) Sanger sequencing

Beckman Coulter Genomics (Takeley, UK) sequenced all PCR amplicons, with capillary sequencing machines. Briefly, the technique consists of a classic PCR (one primer, DNA template and dNTP), in which labeled dideoxynucleotides triphosphates (ddNTP) are added. The 4 ddNTP are each labeled with a different fluorescent dye. When the reaction occurs, the polymerase will randomly incorporate a ddNTP (Figure 15), which will result in stopping the reaction. This stop is due to the absence of a hydroxyl group on the extremity of the ddNTP, so the polymerase cannot link the next nucleotide.

Then, sample is loaded in long and thin acrylic-fiber capillary instead of classic electrophoresis gel. Under electrical field, fragments migrate and are separated by their length. Shorter fragments migrate quicker. At the end of the capillary, a laser stimulates dyes and a camera records the emitted light. To finish, the result is displayed as an electropherogram, with colored peaks corresponding to the DNA sequence (Figure 15).

The 3 primers cited above were used (A4F, A1492R, A71R). So, for each sample, 3 sequences were generated. We choose this combination of primers to have a sufficiently large overlapping area between sequences. That is, sequences generated from A4F and A1492R have to overlap together. Similarly, primers A1492R and A71R have to overlap.

2) Illumina ® sequencing

Illumina is part of the Next-Generation Sequencing (NGS) techniques. The throughput exceeds millions of short sequences per sequencing run. Here, the sequencing of whole genome (WGS) was done on a MiSeq v3 system, in paired-end reads. This consists of sequencing a short fragment of DNA, about bp also called insert , by both ends.

And 300 bp are read from each side.

We choose 48 isolates of Thermococcus for WGS. They were sequenced in 2 runs, with 24 multiplexed genomes per run. The multiplexing allows sequencing multiple samples in one time. To avoid confusing, each library is flanked with a sequencing tag (or index), Then, all steps were performed according to the manufacturer protocol. Briefly, after the shearing, ends of DNA fragments were repaired with both -exonuclease andpolymerase. Next, DNA fragments that have the right size were selected with small magnetic beads. The next step consists of adding an A nucleotide in ends of each fragment, with a ligase. Then adapters were ligated to both sides of each insert. During this step, a specific barcode was allocated to each sample and this will allow multiplexing samples on the same flowcell. Before pooling libraries together, they must go through a validation step. First, the quality was checked with a Bioanalyzer 2100 (Agilent Technologies) (Figure 16). Libraries were loaded on high sensitivity DNA chips (Ref: 5067-4626, Agilent Technologies). In a second time, libraries were quantified by a qPCR protocol (see below). To finish, libraries were normalized to 2 nM, and they were pooled (5 µL of each normalized library).

IV) Sequence assembly

In bioinformatics, sequence assembly is the step where reads are merged together in order to reconstruct a longer sequence.

1) Workflow to recover full 16S-ITS sequences a) 16S-ITS quality check

Before assembling, it is mandatory to check the sequences quality. For the Sanger sequencing technique, Beckman Coulter Genomics provide several reports, in particular whether the sequence passed the sequencer quality filter or not. Then, each sequence came with a file containing the nucleotide sequence and the quality score associated to each position. The sequencer calculates this score following the PHRED format and recommendations (Ewing and Green, 1998;Ewing et al., 1998). Most of the time, the quality of the first 20 to 30 nucleotides of reads is below the threshold of Q30 (99.9% of chance that a nucleotide is assigned correctly). This was reflected in the presence of abnormal peaks (Figure 18), so they were trimmed. The same thing was observed for the end of each sequence. Around position 700 to 800, the quality began to decrease, and it is increasingly difficult to discern the peaks on the electropherogram (Figure 18).

b) 16S-ITS assembly

Here, for each Thermococcales isolate, 3 reads were merged. Assembly step was done with in-house Perl and BASH scripts. First, sequences were trimmed at both ends: from position 1 to 25, and from position 800 to the end. These thresholds were chosen because they were suitable for the vast majority of sequences. Next, sequences arising from primers A1492R and A71R were reversed and complemented with revseq (package EMBOSS v6.5.7.0), because they were in reverse direction. Then, sequences were aligned with each other using MUSCLE v3.8.31 [START_REF] Edgar | MUSCLE: multiple sequence alignment with high accuracy and high throughput[END_REF]. Some public 16S-ITS sequences of Thermococcales were added in the alignment to guide MUSCLE. After that, overlapping areas were analyzed one by one in order resolve conflicts. When a conflict was found, we referred to the electropherogram, and choose between the two possibilities. The software 4Peaks v1.8 (http://nucleobytes.com/4peaks/) was used to visualize electropherograms.

2) Whole genome

The way to reconstruct a whole genome sequenced with short read differs from assembling Sanger reads. The method used is based on the resolution of de Bruijn graphs [START_REF] Compeau | How to apply de Bruijn graphs to genome assembly[END_REF]. The idea is as follow: short reads are decomposed into small pieces of length k, or k-mer. Usually, the value of k is odd and is comprised between 21 and 63 within CLC Genomics Workbench. Then these pieces are aligned.

The prefix (length k-1) of the suffix of the k-mer n has to match exactly with the suffix (length k-1) of the k-mer n+1. Raw reads were sent by the sequencing center. The only processing they did was the de-multiplexing step, which consisted of sorting reads according to the samples and removed traces of Illumina primer and adapters. Each sample came with 2 files: the first containing the read1 of a pair and the second containing the read2 of the same pair, in FASTQ file format, sorted in the same order.

a) Apply quality filter

Like all sequencing methods, Illumina technologies generate some errors during sequencing, at a rate of around 0.1% [START_REF] Glenn | Field guide to nextgeneration DNA sequencers[END_REF]. In addition, the quality of reads decreases as its length increases (Figure 19). So, in order to filter sequencing errors out, empirical algorithm has been released to discard low quality reads [START_REF] Minoche | Evaluation of genomic high-throughput sequencing data generated on Illumina HiSeq and Genome Analyzer systems[END_REF]. This algorithm was transcribed in Python, a very common programming language in bioinformatics. This tool, illumina-utils v1.4.2 [START_REF] Eren | A Filtering Method to Generate High Quality Short Reads Using Illumina Paired-End Technology[END_REF], was employed with the command iu-filter-quality-minoche and default parameters. Furthermore, CLC mapped the reads back on the assembly. Thanks to this, the software calculated the coverage value for every position. If the assembly produced multiple contigs, the Join Contigs tool of the Genome Finishing Module of CLC was used. )t consists of linking ends of 2 contigs using linkage information from paired-end reads and/or BLAST. Sometimes, this method was not conclusive, so other assemblies were undertaken, using different values of k-mer, from 23 to 63 (limit of the software), until reaching the smallest number of final contigs.

V) Phylogenetic tree

A phylogenetic tree is a way to represent evolutionary relationships between individuals. Since the advent of sequencing technics, phylogenetic are built using molecular markers, both DNA and proteins.

1) Assign taxonomy through 16S-ITS phylogenetic tree

From the UBOCC, 273 16S rRNA -ITS sequences of Thermococcales were produced. A way to assign taxonomy to each sequence is to build a phylogenetic tree. First, 16S-ITS sequences of fully sequenced Thermococcales genomes were downloaded from RefSeq database (NCBI), either 20 sequences when the tree was built.

The alignment of sequences was done first with MUSCLE, but this was not conclusive.

We choose to switch to SINA, an aligner designed for 16S rRNA gene sequences, which use the 16S rRNA gene variable and conserved regions (Pruesse et al., 2012). But this tool does not take into account the ITS. So, sequences were cut at the last nucleotide of 16S rRNA gene sequence and thes sequences were aligned with SINA v1.2.11, with the parameter profile set to Archaea. All ITS were aligned with MUSCLE v3.8.31, default parameters. Then both parts of each sequence were concatenated.

The next step was the building of the tree. The method employed was Bayesian phylogeny, with MrBayes v3.2.6 [START_REF] Ronquist | MrBayes 3: Bayesian phylogenetic inference under mixed models[END_REF]. The evolutionary model was HKY (nst=2) (Hasegawa et al., 1985), with an invariable gamma rate (rates=invgamma). The run was composed of 60 000 000 occurrences (ngen=60000000) that were sampled every 2000 times (samplefreq=2000). The first 25% of occurrences were discarded, during the burn-in phase. Then, the tree was visualized with ARB [START_REF] Ludwig | ARB: a software environment for sequence data[END_REF] and FigTree v1.4.2 (http://tree.bio.ed.ac.uk/software/figtree).

2) Second way to assign taxonomy

Taxonomy of each isolate was assigned with another method that is more convenient:

the RDP classifier v2.11, with default parameters (Wang et al., 2007). This tool works by comparing the 16S rRNA gene sequence to a database and return the result with confident index for each taxonomic rank.

3) Phylogenomic tree from rich set of genes

Phylogenomics is the junction of phylogeny and genomics. One aim is to build phylogeny with genomics data, like whole genome DNA or different sets of concatenated genes. Throughout this study, we used Single Copy core-Genes (SCGs).

That is to say, for a given set of genomes, all single-copy genes shared by all genomes. b) Single copy core-genes

The set of single copy genes for the 114 genomes was extracted thanks to the anvi o visualization tool [START_REF] Eren | Anvi'o: an advanced analysis and visualization platform for 'omics data[END_REF] and its pangenomics workflow. The latter is available online (http://merenlab.org/2016/11/08/pangenomics-v2/). Briefly, the pipeline was as follow: Prodigal [START_REF] Hyatt | To assess the completion and redundancy of genomes, we used HMMER v3.1b2 and a set of 162 archaeal single copy genes[END_REF] found the Coding DNA Sequences (CDS) for each genome. Each CDS was annotated thanks to the Cluster of Orthologous Gene (COG) database (Galperin et al., 2014). Then, anvi o ran a BLASTP of all proteins against themselves in order to create a similarity graph [START_REF] Altschul | Basic local alignment search tool[END_REF]. This graph was then parsed using the MCL algorithm (Van Dongen, 2000;[START_REF] Van Dongen | All pangenomes are displayed with the command anvidisplay-pan in anvi o and )nkScape v . was used to for figures refinement[END_REF], with inflation (--mcl-inflation) parameter set to 6 for the global pangenome, in order to create protein clusters (PC). These latter could be regarded as clusters of orthologous genes, depite not being true COGs. If a PC contained at least 1 protein for each genome, it thus belonged to the core genome. In the particular case where a core genome PC contained a single protein from each genome, this PC was considered part of the Single-copy Core-Gene collection (SCGs) c) Phylogenomic tree Phylogenomic tree was built with the concatenation of identified SCGs. First, protein sequences of SCGs were extracted and sorted by PC, one file per PC. So each files contained 114 sequences, 1 for each genome. Then, proteins sequences were aligned with MAFFT v7.055b, in accurate mode (mafft-linsi) [START_REF] Katoh | PhyML v3 was used for the tree, as well as the SMS option to select the best evolution model, and aLRT as bootstrap method[END_REF]. The trimming of sequences was performed with BMGE v1.12, with default parameters [START_REF] Criscuolo | BMGE (Block Mapping and Gathering with Entropy): a new software for selection of phylogenetic informative regions from multiple sequence alignments[END_REF]. The 2 previous steps were carried out for all files independently. To finish the preparation of data, proteins sequences were concatenated with an in-house Perl script. The resulting file was then visually inspected; invariable positions were discarded and the result was saved in PHYLIP format (Felsenstein, 1981) with SeaView 4.6.1 [START_REF] Gouy | SeaView version 4: A multiplatform graphical user interface for sequence alignment and phylogenetic tree building[END_REF].

The phylogeny was built with PhyML v3.20120412 [START_REF] Guindon | A simple, fast, and accurate algorithm to estimate large phylogenies by maximum likelihood[END_REF][START_REF] Guindon | New Algorithms and Methods to Estimate Maximum-Likelihood Phylogenies: Assessing the Performance of PhyML 3.0[END_REF] on a dedicated webserver (http://www.atgcmontpellier.fr/phyml/). The selection of model of evolution was done with SMS, a plugin of PhyML that tested different models and selected the one that best fit the dataset [START_REF] Lefort | SMS: Smart Model Selection in PhyML[END_REF]. The parameters selected were: Akaike Information Criterion as selection criterion; BioNJ as starting tree [START_REF] Gascuel | BIONJ: an improved version of the NJ algorithm based on a simple model of sequence data[END_REF]; NNI as tree improvement;

aLRT SH-like for fast likelihood-based branch support calculation method [START_REF] Anisimova | [END_REF].

The resulting tree was visualized with iToL, a web-based platform [START_REF] Letunic | Interactive tree of life (iTOL) v3: an online tool for the display and annotation of phylogenetic and other trees[END_REF].

VI) Species definition

During this work, two groups were chosen for studying the inter-specific genomic diversity of archaeal populations. This implied to highlight species present in our dataset of 114 genomes.

1) Average Nucleotide Identity

A wildly used method to perform this task relies on the ANI between pairs of genomes.

This implies that close relative microorganisms have less divergent ANI values than two more distant microorganisms. A value of ANI greater than 94-96% implies that both microorganisms belong to the same species. This value was computed for all pairs within the dataset of 105 genomes, either 11 025 pairs. OrthoANI v1.2 was used to compute all pairs (Lee et al., 2015). This software employed the BLAST-based method to calculate ANI instead of the MUMmer-based method.

All results were compiled in a square matrix. The heatmap was built with R v3.2.2 (R Core Team, 2015) and the package gplots v3.0.1 (function heatmap.2), using RStudio (https://www.rstudio.com/).

2) In silico DNA-DNA hybridization

The in silico DNA-DNA Hybridization (DDH) is another way to define microbial species.

The value of 70% is accepted as the threshold at which 2 microorganisms are defined as belonging to the same species. In general, this threshold corresponds to the ANI 94-96%. But two combined metrics are more accurate than one.

In silico DDH was computed with the Genome to Genome Distance Calculator (GGDC) v2. 1 (Auch et al., 2010a, 2010b[START_REF] Meier-Kolthoff | Genome sequence-based species delimitation with confidence intervals and improved distance functions[END_REF][START_REF] Meier-Kolthoff | All heatmap were built with R v3.2.2 (R Core Team[END_REF]. The web service was used to achieve this step, with default parameters (http://ggdc.dsmz.de/ggdc.php).

VII) Searching specific PC in both groups of close genomes

In order to find genomic markers for closely related clades, we defined specific proteins clusters (SPC): these are PC that belongs only to a monophyletic subset of genomes.

SPCs were indentified by carrying a new pangenomics analysis for both groups of isolates. The difference with the pipeline applied previously for pangenomics was the parameter --mcl-inflation, set to 8.

1) COG and KEGG annotations

We annotated each gene by comparison to the COG database using anvi o (anvi-runncbi-cogs). Then, for a given sub-group, all genes present in SPCs were annotated with the KEGG Automatic Annotation Server (KAAS) [START_REF] Lefort | All trees were visualized on iToL (Letunic and Bork, 2016). All gene were also annotated with the KEGG Automatic Annotation Server (KAAS) to recover metabolic pathways, using the Best BLAST Hit method and following list of organisms as reference: hsa, dme, ath, sce, pfa, eco, sty, hin, pae, nme, hpy, rpr, mlo, bsu, sau, lla, spn, cac, mge, mtu, ctr, bbu, syn, aae, mja, afu, pho, ape, ton, tko[END_REF]. The aim of this annotation was to identify metabolic reactions only present within a cluster of genomes.

KAAS was used with the Best BLAST Hit (BBH) method. The parameter gene" was modified to compare all SPCs to genes belonging to the following list of organisms: hsa, dme, ath, sce, pfa, eco, sty, hin, pae, nme, hpy, rpr, mlo, bsu, sau, lla, spn, cac, mge, mtu, ctr, bbu, syn, aae, mja, afu, pho, ape, ton, tko, tga, tsi, tba, pab, pfu. After computation, identifiers (ko ids) were available for each gene, unless KAAS did not found an annotation.

Then each SPC with a ko id was compared to all genomes from the same pangenome, at different levels. First, we searched for the presence of the same ko id within all PC from the pangenome. Then COG annotations were used in the same way as the ko ids: we searched for SPCs that have a unique COG annotation through the entire pangenome.

VIII) Metapangenomics

Metapangenomics is a strategy to study pangenomes conjunction with metagenomes to simultaneously identify gene clusters across closely related genomes and characterize their occurrence in the environment through metagenomic data. During this step, we reviewed the bibliography for the presence of deep-sea hydrothermal vents metagenomes. The aim of this part was to estimate the distributions of Thermococcales genomes in this kind of extreme environment.

1) Recovering metagenomes

Metagenomes used in this work were retrieved from the database Sequences Reads Archive (SRA), hosted by the NCBI. The whole database was browsed with keywords such as hydrothermal , hydrothermal vent or deep-sea metagenome . )n total, metagenomes sequenced by Illumina technologies were recovered (Appendix 2). Most of them came from deep-sea hydrothermal environments. Eighteen were hot-spring metagenomes, from Yellowstone national park, South Africa or Taiwan.

2) Processing of metagenomes a) Download

An in-house BASH script was designed to automatize the whole process. First, metagenomes were downloaded in sra file format. This format had to be converted before use. This was done with the SRA toolkit v2.8.2. The command prefetch downloaded the file from the NCBI SRA database (with the parameter -v <SRA-id>).

Then, the file was decompressed in FASTQ format, with the command fastq-dump. The argument --split-files allowed to split the dataset in two files containing read 1 and read 2 respectively.

b) Quality

On each pair of file, the Minoche quality filter was applied using illumina-utils, as for genome assemblies (IV.2.a).

c) Mapping of reads to genomes

After the quality filtering, reads were mapped on genomes, with Bowtie v2. 3.1 (Langmead and Salzberg, 2012). Before running bowtie, all data on which we wanted to recruit reads were grouped within a single file. Then the command bowtie2-build was applied to this file. This generated the index, a list of files used by bowtie to map reads.

Then, each pair of metagenome reads was mapped on the target genomes. It produced an alignment file in sam format (Sequence Alignment/Map). For downstream analysis, it was preferable to have a sorted and indexed alignment file. This was done with SAMtools, v1.3.1 [START_REF] Li | The Sequence Alignment/Map format and SAMtools[END_REF]. First, the sam alignment file was converted in bam file (Binary Alignment/Map) with samtools view. Then it was sorted with the command samtools sort and indexed with samtools index. At the end, we have one sorted and indexed file for each metagenome. This file was then processed with anvi o, following profiling and merging steps presented in the following workflow described online (http://merenlab.org/2016/06/22/anvio-tutorial-v2/).

First with anvi-profile we synthetized the information for each mapping result on each genome. That is to say, for a given position, it recovered which read mapped and which nucleotide. This was done for the 354 metagenomes separately. Then, all profiles were merged with anvi-merge function. This allowed the visualization of all metagenomes mapped on the same genomes simultaneously.

3) Visualization of data

For all metagenomes mapped on genomes, anvi o calculated multiple metrics. The one that interested us was the detection . It is the ratio of position on a given genome that was mapped divided by the total length of the genome. For example, 1% of detection on a 2 Mbp genome corresponds to 20 000 distinct positions of this genome were found within the metagenome.

Results

Chapter III: Results

I) Screening culture collection for Thermococcus

1) Abstract

Investigating genomic markers of early diversification requires a collection of closely related microorganisms in order to highlight clade-specific genes and pathways. The LM2E owns a collection of marine microorganisms, sampled during multiple oceanographic cruises. Among the 1300 isolates available in this collection, 305 are classified as Thermococcales based on phenotypes features and microscopic observations. In this study, we built a phylogenetic tree based on 16S rRNA genes and 16S-23S spacer (=ITS). Two groups of isolates were then selected based on their multiple geographic origins and phylogenetic placement. In total, this represents 48 isolates suitable for genome sequencing in order to investigate genomic diversity between closely related Thermococcus isolates.

2) Introduction

The genomic diversity of microorganisms is nearly infinite. Bacteria and Archaea are present in nearly all environments on Earth, including the deep-sea hydrothermal vents, and are adapted to these habitats. These adaptations imply a large gene catalogue, spread in both Bacteria and Archaea. Indeed, pangenomics studies show a continuously increasing number of new genes when the number of compared genome increases, at the genus taxonomic level (Tettelin et al., 2005(Tettelin et al., , 2008)). This study will focus on the identification of closely related microorganisms from an extreme environment, the deep-sea hydrothermal vents (DSHV), with the perspective to study genes and pathways associated with early differentiation and / or speciation stages.

DSHV are complex and dynamic structures from geochemical and biological aspects (Wang et al., 2009). They are formed by precipitation of minerals and metals contained in a hot and reduced fluid, which results from leaching of rocks from the oceanic crust.

DSHV are mainly present in two types of geochemical contexts: ultramafic and basaltic (Wetzel and Shock, 2000). The first is characterized by high concentration of H2 and CH4 and low H2S, while it is the opposite for basaltic DSHV (McCollom, 2007). This particular environment, hot and reduced fluid opposed to cold and oxygenated seawater, offers many ecological niches due to the presence of sharp physico-chemical gradients.

Microbial communities associated to DSVH are composed of chemolithoautotrophs that act as primary producers and allow the presence of a wide diversity of bacterial and archaeal heterotrophs (Jannasch and Wirsen, 1979;[START_REF] Roussel | Comparison of microbial communities associated with three Atlantic ultramafic hydrothermal systems[END_REF]. DSHV are widespread in oceans, but microbial communities associated with them show high degree of similarities (Anderson et al., 2015). Even if it is possible for Thermococcales to migrate between sites and colonize newly formed chimneys (Pagé et al., 2008), they arrive to a new site by chance, possibly following currents [START_REF] Wirth | Colonization of Black Smokers by Hyperthermophilic Microorganisms[END_REF]. In the case of geographic distant isolates, this should have an impact on the gene flow, with apparition of dispersal barriers. The result is the separation and diversification of populations (Shapiro et al., 2012).

At the LM2E, there are continuous efforts to build a culture collection that can be used to address fundamental questions that we are interested in going after in this dissertation. The UBOCC culture collection comprises hundreds of isolates of marine microorganisms, originating from different places around the world and sampled during different oceanographic cruises. From this culture collection, around 300 isolates are classified as Thermococcales, a hyperthermophilic Archaea living primarily within hot marine ecosystems like deep-sea hydrothermal vents (Zillig et al., 1983(Zillig et al., , 1987)). The order of Thermococcales comprises three genera: Pyrococcus, Palaeococcus and Themococcus (Fiala and Stetter, 1986;Takai et al., 2000;Zillig et al., 1983). To date, 45 characterized species are documented within the Thermococcales, of which 34 belong to Thermococcus. In this study, we will focus on Thermococcus, because they are well studied, easy to grow and isolate. Moreover, genetic tools are available (Thiel et al., 2014), they harbor mobile genetic elements [START_REF] Cossu | Flipping chromosomes in deep-sea archaea[END_REF][START_REF] Gaudin | Extracellular membrane vesicles harbouring viral genomes[END_REF]Gorlas et al., 2012), and they are more abundant than the two other genera (Huber et al., 2006;[START_REF] Lepage | Molecular diversity of new Thermococcales isolates from a single area of hydrothermal deep-sea vents as revealed by randomly amplified polymorphic DNA fingerprinting and 16S rRNA gene sequence analysis[END_REF]).

Here we report the framework for taxonomic assignment of Thermococcales isolates present in the UBOCC culture collection. The strategy employed was to sequence the 16S rRNA gene marker and also the 16S-23S rRNA internal transcribed spacer (ITS).

The 16S rRNA gene allowed the taxonomic affiliation of each isolate, while the ITS was used to discriminate between closely related isolates [START_REF] García-Martínez | Prevalence and microdiversity of Alteromonas macleodii-like microorganisms in different oceanic regions[END_REF]Huber et al., 2006). Indeed, thanks to its broad sequence and length polymorphism, the ITS locus is widely employed in marine bacterial and archaeal population studies [START_REF] García-Martínez | Microdiversity of uncultured marine prokaryotes: the SAR11 cluster and the marine Archaea of Group I[END_REF][START_REF] García-Martínez | Prevalence and microdiversity of Alteromonas macleodii-like microorganisms in different oceanic regions[END_REF]. With the sequencing of the ITS, we expect to increase phylogenetic tree robustness. The purpose of this tree is to act as a support for selecting groups of isolates for genome sequencing to inspect the genomic diversity of closely related Thermococcus isolates.

3) Results

a) Origins of isolates

All strains used in this work were stored at -80°C in the culture collection hosted in the laboratory. Among thousands of isolates, 305 strains were predicted to belong to the order of Thermococcales based on microscopic observations and growth culture condition. We cultivated each isolates, extracted the DNA and we sequenced their 16S rRNA gene and ITS sequences. Among these, 95 sequences of 16S rRNA gene were already available in the lab. On the 305 isolates available, 32 sequences of 16S-ITS could not be obtained, due to a failure at the cultivation step, or presence of contamination in the culture (multiple peaks on the electropherograms). Therefore, we have retained 273 full sequences of 16S-ITS (Appendix 1). These isolates originated respectively from: the Pacific Ocean, with 77 isolates from the East Pacific Rise (EPR) 13°N and 121 from the EPR 9°N; the Atlantic Ocean, with 40 isolates from the hydrothermal field Rainbow and 8 from the hydrothermal site Menez-Gwen; 12 isolates from the Indian Ocean; 4 from the Antarctic island Saint-Paul (South Indian Ocean); and 11 without geographic origin (Appendix 1). After the 16S rRNA gene sequences taxonomic assignment, 14 isolates were assigned to the order Pyrococcus, and the other 259 isolates were all assigned to the Thermococcus order (Appendix 1).

In order to verify this taxonomic assignment and choose isolates for genome sequencing, we built a phylogenetic tree. As specified above, sequences used were: the 16S rRNA gene sequences and the ITS sequences of the isolates sequenced during this study, and also the 16S rRNA gene and ITS sequences available in the public databases,

i.e. from sequenced genomes. Both alignments were merged and the figure 20 shows the resulting tree.

On this phylogenetic tree, 2 groups of closely related clades were chosen for whole genome sequencing, based on the following criteria: (i) geographic origin of the isolates.

We decided to select in priority groups composed of isolates from multiple geographical origins (hydrothermal fields) in order to address the question of impact of dispersion on the gene flow between sites. (ii) There must be several isolates for each geographical origin. The group should appear monophyletic, meaning with a putative common ancestor to all isolates. Ideally, a group should be composed approximately of 24 genomes (for a total of 48 genomes sequenced). We also considered the presence of potential mobile genetic elements (plasmids, viruses) by targeting isolates close to known strains with plasmids such as T. nautili, because these elements can act as drivers of evolution

The first group included 21 isolates from the Pacific Oceannamely the EPR 13°N -, the Atlantic Oceannamely the Rainbow and Menez Gwen sitesand the South Indian

Oceannamely the Saint-Paul island -(Figure 20; Figure 21). This group was close to Thermococcus sp. 4557. All isolates come from deep-sea hydrothermal vents, except the 4 that originate from Saint-Paul, which were sampled from a shallow hot spring.

The second group was composed of 27 genomes (Figure 20, Red isolates). Here, isolates come from the 2 sites in the Pacific Ocean, the EPR 9°N and the EPR 13°N (Figure 21).

This group was also chosen because isolates are closely related to T. nautili. Indeed, this strain harbors 3 plasmids that can potentially serve as a vector of genetic information between isolates (Oberto et al., 2014).

4) Discussion

In this study, our purpose was to select groups of closely related isolates for later investigation of their genomic diversity. We thus choose to sequence 16S rRNA gene sequences and 16S-23 rRNA gene spacers (ITS) to place nearly 300 strains in a phylogenetic context. The ITS spacer is not under a selection pressure because it is a non-coding sequence and usually exhibits a higher variability and can improve phylogenetic resolution. Moreover, this ITS shows patterns of biogeography between isolates of Thermococcus sampled in the Pacific Ocean (Huber et al., 2006). Other studies also showed these biogeographic patterns in Thermococcus [START_REF] Lepage | Molecular diversity of new Thermococcales isolates from a single area of hydrothermal deep-sea vents as revealed by randomly amplified polymorphic DNA fingerprinting and 16S rRNA gene sequence analysis[END_REF]Price et al., 2015).

From the collection of 273 sequenced isolates, 2 groups of closely related isolates were selected. Group I validated all our selection criteria. Indeed, the 21 isolates were from the Atlantic, the Pacific and the South Indian Oceans. Group II validated the two first criteria, which are multiple isolates from multiple origins. Only 12 isolates were monophyletic at the 16S rRNA gene-ITS level. But the 27 isolates composing group II were all close to Thermococcus nautili, the isolate cited above which harbors 3 plasmids [START_REF] González | Thermococcus nautili sp. nov., a hyperthermophilic archaeon isolated from a hydrothermal deep-sea vent[END_REF]. One of those plasmids code for an integrase, and this protein was

shown to be responsible for shuffling the strain chromosome [START_REF] Cossu | Flipping chromosomes in deep-sea archaea[END_REF]. For authors, this can be a mean of rapid adaptation to environmental changes. Indeed, this shuffling could place genes in a different genomic context, what may cause repression or activation, which can lead to isolates with higher fitness or abilities to colonize a new ecological niche.

5) Conclusion

To conclude this work, we started from 305 isolates of Thermococcales present in the UBO Culture Collection. Now nearly all isolates have a taxonomic assignment, and a phylogenetic tree was built with the concatenation of 16S rRNA gene and ITS sequences of each isolates. We selected two groups of Thermococcus, composed of 21 and 27

isolates. Genomes of these 48 isolates will be fully sequenced to study their genomic diversity.

6) Materials and Methods

All strains were cultured anaerobically in penicillin vials using two media, TRM [START_REF] Zeng | Pyrococcus CH1, an obligate piezophilic hyperthermophile: extending the upper pressure-temperature limits for life[END_REF] and Ravot (Gorlas et al., 2013), depending on the isolates.

Genomic DNA of each isolate was extracted using a classic phenol-chloroform technique, with 50mL of fresh culture. Briefly, centrifuge culture at 8 000 rpm for 5 min at 4°C and discard supernatant. Homogenize the cell pellet with 1mL of TNE 1X buffer

II) Comparative genomics of closely related isolates to identify genetic and genomic markers of diversification 1) Abstract

The hyperthermophilic archaeon Thermococcus is always present in deep-sea hydrothermal vents. It is also a pioneering species during the colonization of new deepsea chimneys. In the laboratory, it can be easily cultivated and new strains are isolated on a regular basis. In a previous study, we selected two groups of around 24 isolates from different geographical locations and sequenced their genomes. Isolates from group I originated from Pacific, Atlantic and South Indian Oceans, whereas group II isolates were sampled in two locations from Pacific Ocean (EPR). Here we are interested in the genomic diversity of closely related isolates, to identify markers of differentiation and pinpoint genes and pathways involved in this differentiation. To answer this, we used both pangenomics and phylogenomics with all genomes of Thermococcales available.

From group I, isolates are well clustered by their geographic origin, and each cluster corresponds to a microbial species, while isolates from group II do not follow this trend.

This second group contains 6 distinct species, among which 2 are present on two hydrothermal sites. Globally, many clade specific genes are involved in amino acids, energy and carbohydrates metabolisms, which must reflects selection pressure that these organisms encounter in hydrothermal environments. For geographically distant isolates, the distance parameter is a driver of diversification, which probably translates into a decrease or absence of gene flow, while niche partitioning should explain intrasite patterns observed in the group II. All specific genes highlighted here can serve as targets for future genetic studies.

2) Introduction

Deep-sea hydrothermal vents (DSHV) host a huge diversity of microorganisms.

However, this environment is described as extreme, due to the high hydrostatique pressure and hot hydrothermal fluid. In addition to the large geochemical gradients present, DSHV are dynamic geochemical and biological structures (Anderson et al., 2017b;Wang et al., 2009). Consequently, microorganisms have to adapt to quick environmental changes in their ecological niche.

Genomes of DSHV microorganisms are highly variable. A study reported that deep-sea metagenomes are enriched with mobile genetic elements such as genes encoding transposases [START_REF] Brazelton | Abundant transposases encoded by the metagenome of a hydrothermal chimney biofilm[END_REF], suggesting a need for adaptation over short periods of time. For example, the Archaea Thermococcus nautili harbors three plasmids, of which one code for an integrase. This particular protein is involved in the chromosome dynamics and shuffling of its host [START_REF] Cossu | Flipping chromosomes in deep-sea archaea[END_REF]. Authors proposed that this rapid reorganization of the chromosome can acts on the fitness of a particular genome within the population. In general, Thermococcales harbor a large number of mobile genetic elements, plasmids or viruses, potentially involved in genetic transfers between isolates [START_REF] Erauso | Sequence of plasmid pGT5 from the archaeon Pyrococcus abyssi: evidence for rollingcircle replication in a hyperthermophile[END_REF]Gorlas et al., 2012;Krupovic et al., 2013;Wagner et al., 2017). Moreover, Pyrococcus genomes show extensive rearrangements, and presence of horizontal gene transfer [START_REF] White | Extensive Genome Rearrangements and Multiple Horizontal Gene Transfers in a Population of Pyrococcus Isolates from Vulcano Island, Italy[END_REF]. While Thermococcus genomes are diverse and dynamic, core functions are conserved in the same genomic context [START_REF] Cossu | Comparative genomics reveals conserved positioning of essential genomic clusters in highly rearranged Thermococcales chromosomes[END_REF].

The genomic diversification depends on multiple mechanisms, notably the gene flow between isolates (Cordero and Polz, 2014;Shapiro et al., 2012). In case of sufficiently high rate of gene flow, the population should stay homogeneous, but the establishment of barriers will result in the emergence of at least two new species, populations or ecotypes [START_REF] Cohan | A Systematics for Discovering the Fundamental Units of Bacterial Diversity[END_REF]Fraser et al., 2009;Shapiro et al., 2012). There are several barriers, like colonization of a new ecological niche or geographic isolation (Anderson et al., 2017a;[START_REF] Cadillo-Quiroz | Patterns of gene flow define species of thermophilic Archaea[END_REF]Whitaker et al., 2003).

Here we aimed at identifying genomic markers of diversification in closely related isolates of Thermococcus subjected to different drivers of diversification. Thus, we pinpointed genes and pathways involved in this differentiation to learn more about the selection pressures that apply to these isolates. For sympatric isolates, specific loci accounting for differences between evolutionary adjacent clades (species or populations) are indeed likely to be those under selective pressure. Their function should therefore inform about the evolutionary processes leading to population differentiation and eventually, speciation. For allopatric isolates, those clade-specific loci will provide insights about the effects of gene flow limitations on early genomic differentiation, e.g. what are the loci most sensitive to genetic isolation.

In this work, we used a pangenomics approach to establish a phylogeny based on core genome of all Thermococcales genomes available at the time of this study. This approach allowed defining de novo a set of genes for building a phylogenomic tree. It thus represents an improvement over methods relying on universal SCGs gene sets like AMPHORA of PhyloSift [START_REF] Darling | PhyloSift: phylogenetic analysis of genomes and metagenomes[END_REF][START_REF] Wu | A simple, fast, and accurate method of phylogenomic inference[END_REF] as it strongly improved the robustness of the phylogenomic reconstruction.

In addition, this set of genes was selected without a priori about functions, because it was based on the core-genome, which are all genes shared by all genomes considered (Tettelin et al., 2005). In pangenomics, the core-genome is opposed to the accessory genome (also called specific genome), which include all genes not shared by all studied genomes. The union of the core-and accessory-genomes represents the pan-genome.

The size of the core genome relies on the number of genomes included in the comparison. Indeed, the number of shared (core-) genes decreases with the addition of new genomes within the comparison, until reaching a plateau, whereas the size of the pan-genome can constantly increase (Tettelin et al., 2005;Touchon et al., 2009). In this study, we reconstructed a phylogeny based on core-genes that are present in single copy within these Thermococcales genomes. We then applied this pan-genomics approach to perform comparative genomics analysis and identify protein cluster that are differentially represented in closely related clades.

3) Results

a) Genome sequencing and assembly

We constructed and sequenced Illumina libraries for each of the 48 genomes selected in a previous study. Among all genomes, 19 were circular, 15 were available in one linear contig, and 13 genomes were assembled in a number of contigs ranging from 2 to 57 (Table 5). We then looked for the presence of putative plasmids in the genomes sequenced here. A contig is considered as a potential plasmid if the coverage of the latter is at least 3 times greater than the average coverage of the chromosome (Figure 22). In total, 17 contigs are potential plasmids. Moreover, we expect the presence of such mobile genetic element integrated in two genomes, T. sp EXT10c and T. sp EXT11c, For T. sp EXT11c, we observed a sharp increase in coverage between positions 398 000 and 412 000, from 230X on average in the genome to 3000X between these positions (Figure 22). The same observation was made for T. sp EXT10c: the coverage increase from 200X to 650X between positions 1 896 100 to the end (1 909 014). Of these 48 sequenced genomes, only 45 were used for the pan-genomics analysis of group I and group II isolates. The IRI06c isolate genome was assembled into 9 contigs. It was expected to be closely related to Thermococcus nautili (16S-ITS phylogenetic tree), but on a core-genes based tree, IRI06c was no longer close to T. nautili. About this isolate, the 16S rRNA gene data was already available in the laboratory. We sequenced the ITS with DNA already extracted. However, we found 15 different nucleotides between the previously known 16S rRNA gene sequence and the one from the fresh cultured IRI06c genome, indicating that they are different isolates. Nevertheless, this genome will be integrated in the Thermococcales pan-genome. For the MC5 strain, the raw data contained only sequences for PhiX, a control used on Illumina sequencing systems. Several reasons may be advanced: a mistake may have occurred during the library preparation, nevertheless the library passed quality and quantity controls.

Alternatively, the error may have occurred during the demultiplexing step, with a mistake in the barcode assignation. The last non-exploitable isolate was E15P25. In this case, the total length of assembled contigs was 4Mb, which is about twice the average length of a standard Thermococcus genome. Within the 29 contigs, a set of 162 archaeal genes that should be present in single copy [START_REF] Rinke | Insights into the phylogeny and coding potential of microbial dark matter[END_REF] were duplicated. Two ribosomal operons were also present. This strongly suggests the presence of two genomes within this sample, harboring the same 16S rRNA gene sequence and therefore an incomplete isolation of this strain or a contamination during growth experiment.

Concerning the other sequenced genomes, their average length is 2.02 Mbp, with a minimum of 1 876 541 bp (AMTc95) and a maximum of 2 230 429 bp (MC8). The gene number is on average 2 219 genes, with a minimum of 2 076 genes (AMTc95) and a maximum of 2 536 genes for MC8. The G+C content is on average 54.82%. Genomes with the lowest G+C content are AMTc51-52, with 53.93%. And the genomes with higher G+C content are AMTc70-71-72-73, with 55.96% (Table 5).

b) Definition of closely related clades: what is the evolutionary history of our genomes?

The first step in our study was to place sequenced genomes within an evolutionary context. Here, we decided to use the largest set of genes common to all genomes, i.e the core-genome, instead of a predefined or universal set of genes to build a phylogenomic tree based on a set of Single-copy Core Genes SCGs . To recover these genes, we decided to use a comparative genomics approach to obtain the pan-genome, and from this latter, identify SCGs without a priori knowledge of their annotation..

The figure 23 is a representation of this pan-genome. It is composed of 114

Thermococcales genomes, distributed as follow: 2 Palaeococcus, 17 Pyrococcus and 95

Thermococcus. All these genomes come from: (i) public databases (Table 2,6), (ii) this study (Table 5) or (iii) unpublished genomes sequenced by the laboratory MBGE from Pasteur )nstitute Paris, France . The name of these latters starts with Bxx x (Table 6).

This analysis grouped all 246 617 predicted proteins in 13 431 protein clusters (PCs).

Among them, 778 PC belonged to the core genome (90 611 genes), of which 602 PCs represented SCGs, highlighted in light blue (Figure 23). Completion and redundancy for the 114 genomes was also evaluated based on a set of 162 archaeal genes that should be present in a single copy in any Archaea as defined by REF. Regarding completion, 90 genomes were complete. The 24 remaining genomes harbored completion between 99.38% and 97.53%, meaning that 1 to 4 SCG were missing (Figure 23). On the other hand, the redundancy in all genomes spanned from 2.47% to 6.17% respectively, meaning that 4 and 10 genes were found at least duplicated (Figure 23). one or more single-copy genes in a genome [START_REF] Eren | Anvi'o: an advanced analysis and visualization platform for 'omics data[END_REF]. Then, layers or genomes are organized based on a phylogeny (top right tree). Besides, we highlighted groups of PC based on their frequency: In blue, all core genes, including in light blue the subpart of SCGs. The three shades of red represent the accessory genome, divided in tree by their relative frequency.

c) From pan-genome to phylogenomic tree

The 16S rRNA gene and the rest of the genome have different molecular clocks (Case et al., 2007). In addition, this marker gene lacks phylogenetic resolution for

Thermococcales. We therefore used genomic information to build a phylogenomic tree.

This tree (Figure 24A) was built by maximum likelihood from the concatenation of protein sequences from the 602 SCGs. The alignment matrix was composed of 157 675 AA positions, of which 92 510 were not redundant.

Concerning the tree topology, regarding the taxonomy of isolates used to build it, three major clades are present. A first grouped all Pyrococcus, a second mixed together the two Palaeococcus genomes plus Thermococcus with a low G+C content (see Figure 23), and the last was composed of all other Thermococcus.

On this tree, all isolates sequenced in this study are separated in two different groups, as expected with the 16S rRNA gene phylogenetic tree. All group I genomes (20) clustered together (Figure 24B), with also two genomes from the public databases: T.

sp. 4557 and T. celericrescens. In this group, the diversification pattern is concomitant with the strains geographical origin. Concerning the group II, all 25 genomes clustered with a reference strain, T. nautili, and with unpublished isolates Bxx x"), for a total of 34 genomes (Figure 24B, Tables 5,6). Interrestingly, the history (=phylogenetic relationship) of these isolates is not correlated with their geographic origin. On the phylogenomic tree, both groups of selected isolates were monophyletic and well supported, and were thus suitable for the genomic diversity study of these closely related isolates. We then carried out two pangenomics studies. There, we only focused on within group genomes (group I & II as defined in this study). All plasmid-contigs have been removed, except for integrated mobile genetic elements.

Since both groups are well supported and monophyletic in the phylogenetic tree, we inspected if geographical isolation could explain their differentiation, and in a second time, wether each group correspond to new species or subspecies. To investigate this, we first considered the tree topology, and then used two metrics: the Average Nucleotide Identity (ANI) and in silico DNA DNA hybridization (DDH), with the thresholds 96% and 70% respectively.

On the phylogenomic tree, group I isolates formed 6 different clusters. Each of these monophyletic groups was matching a different geographical origin (Figure 24B), suggesting a differentiation pattern based on allopatry. In addition, strains originating from the Rainbow hydrothermal vent formed 2 distincts clades, suggesting sympatric differentiation event.

According to AN) and DD(, isolates AMTc from EPR °N formed a species; isolates MC from Saint-Paul also represented a new species, and isolates from Menez-Gwen too (Figure 25A, C . The species T. sp IRI-refer to these three strains from Menez

Gwen. Isolates from Rainbow were organized in 2 distinct clades (Figure 24B, light-blue branches). The 10 IRI isolates from Rainbow (07c, 09c, 10c, 14c, 15c, 24c, 25c, 26c, 27c2 and 29c) had ANI values higher than the threshold generally accepted for species delineation, namely 96% (Figure 25A). Within these 10 isolates, two groups emmerged.

They were, on the one hand, T. sp. IRI24c, T. sp. IRI26c, T. sp. IRI27c2, T. sp. IRI29c, named T. sp IRI-, and on the other hand, T. sp. IRI07c, T. sp. IRI09c, T. sp. IRI10c, T.

sp. IRI14c, T. sp. IRI15c and T. sp. )R) c, named T. sp IRI-Figure 5A). ANI values were close to 100% within these clades and closed to 96.5% between them. Based on DDH, T. sp IRI-2 and T. sp IRI-3 formed two species (Figure 25C).

The geographic origin of group II isolates could not explain the observed tree topology (Figure 24B). In this group, we could define 6 species (Figure 25B After establishing clades of closely related strains, we used comparative genomics on each group, to highlight genes and pathways involved in these differentiation processes.

The presence of specific genes may be the result of (i) a reduction in genetic flow due to geographical isolation (possibly due to allopatric differentiation) or (ii) colonization of a new ecological niches (sympatric differentiation). We conducted a pan-genome analysis on group I and II strains separately. In this framework, we indentified PCs specific to previoulsly defined clades, and focused on the functions present in these specifics PCs (SPC). We only took in consideration functions that were uniq to a clade, implying that the function was absent from the rest of the pan-genome.

i) Group I pan-genome

This pan-genome grouped 49 945 genes within 22 genomes (Figure 26). All these genes were pooled within 3 948 PCs. The pan-genome was organized as follow: 1 459 PCs in the core-genome (32 568 genes), of which 1 352 PCs were only composed of SCGs (29 744 genes). Then the accessory genome was composed of 2 489 PCs, grouping 17 377 genes. Although the accessory genome grouped two-thirds of PCs, it only represented one-third in terms of genes number. All SPCs resulting from differentiation events were present in this accessory genome.

Here, we first investigated species SPCs. All studied bins of SPC are highlighted on the pan-genome figure (Figure 26). For T. AMTc isolates, 153 SPCs were found, of which 1 was involved in cell cycle, 3 in amino acid (AA) metabolism, 1 in transcription, 1 in cytoskeleton, 1 in secondary structure and 4 poorly characterized (Table 7). For the T.

MC isolates, 283 SPCs were present, of which, 5 functions were involved in energetic metabolism, 29 in AA metabolism (Histidine and Tryptophan full biosynthesis pathways), 3 in nucleotide metabolism, 3 in carbohydrate metabolism, 2 in coenzyme metabolism, 2 in translation, 1 in transcription, 5 in inorganic ion transport, and 1 was of unknown function. T. sp. 4557 had 148 SPCs, and following functions were present: 1 was involved in chromatin structure and dynamics, 3 in energy metabolism, 1 in cell cycle, 2 in carbohydrate metabolism, 1 in membrane biogenesis, 2 in secondary structure and 2 were poorly characterized. T. celericrescens had 336 SPCs, and 2 had functions involved in energy metabolism, 2 in carbohydrate metabolism, 1 in replication and repair, 2 in membrane biogenesis, 2 in post-transcriptional modification, 1 in signal transduction, 1 in defense mechanism, 1 was related to mobile genetic element, and 7

were poorly characterized (Table 7). In species T. sp. IRI-1, there were 68 SPCs, comprising only 1 function that was only present within this species, but belonging to a poorly characterized COG category (Table 7). Among the 73 SPCs found in T. sp. IRI-2, no SPC carried known function. Finally, T.

sp. IRI-3 had 71 SPCs and only 1 had a specific function, related to the translation mechanism (Table 7).

Then, among all from Rainbow hydrothermal vent isolates (T. IRI), no specific function was found among the 48 SPCs.

ii) Group II pan-genome

The group II pan-genome included 34 Thermococcus genomes, of which 25 were sequenced for this study, 1 was the reference strain T. nautili plus a re-sequencing of this strain and 7 genomes came from unpublished data (Figure 27, Tables 2,5,6). In total, this pan-genome was composed of 4 255 PCs (74 782 genes) organized as follow:

1425 PCs (48 955 genes) present in the core-genome, whose 1 364 are SCGs (46 376 genes). The accessory genome was composed of 2 830 PCs, grouping 25 827 genes. For this pan-genome, we can make the same observation as for the group I pan-genome:

nevertheless, even if the accessory genome represented two-thirds of PCs, it only grouped one-third of the total number of genes. We then highlighted SPCs for each species and find species-specific functions (Figure 27). The first species grouped 15 isolates (T. sp. E15P35, T. sp. E15P30, T. sp. E15P29, T.

sp. E15P6, T. sp. E15P33, T. sp. AMTc94, T. sp. AMTc79, T. sp. E10P7, T. sp. E10P8, T. sp. E10P11, T. sp. 29-3, T. sp. 33-3, T. sp. 9-3 and two T. nautili), and possessed 15 SPCs, with no assigned specific function (Table 7). The second species grouped 4 isolates (T.

sp. AMTc102, T. sp. AMTc29, T. sp. AMTc09 and T. sp. 26-2) that shared 158 SPCs.

Among them: 5 functions related to AA metabolism, 1 to carbohydrate metabolism, 1 to coenzyme metabolism, 2 to translation metabolism, 1 to post-transcriptional processes, 1 to inorganic ion metabolism and 7 corresponds to poorly characterized functions (Table 7). The third species grouped 9 isolates (T. sp. AMTc19, T. sp. AMTc95, T. sp.

AMTc85, T. sp. AMTc30, T. sp. AMTc67, T. sp. EXT08c, T. sp. EXT09c, T. sp. EXT10c and T.

sp. EXT11c), and only 1 SPC without specific function (Table 7). The fourth species grouped 2 isolates (T. sp. AMTc51 and T. sp. AMTc52). There were 124 SPCs, encoding for the following specific functions: 1 was assigned to RNA processing and modification, 3 to carbohydrate metabolism, 1 to inorganic ion metabolism, 1 to intracellular trafficking, secretion and vesicular transport, and 4 were poorly characterized functions. The fifth species grouped 2 isolates (T. sp. EXT12c and T. sp. EXT13c). 156

SPCs were found, among them, 14 corresponded to specific functions related to AA metabolism, 2 to carbohydrate metabolism, 2 to coenzyme metabolism, 2 to mobilome (= mobile genetic elements) and 1 was poorly characterized. To finish, the sixth species was composed of the isolate Thermococcus sp., of which 36 SPCs displayed 1 specific function related to replication, recombination and repair, 1 to mobilome and 1 was annotated as poorly characterized (Table 7).

Table 7: Specific protein clusters and classification of specific functions

Clades

4) Discussion

In this work, we studied the consequences of differentiation between closely related isolates at the genomic level. We sequenced 45 new Thermococcus strains, present on two different branches on the Thermococcales phylogenetic tree (Figure 24A). We [START_REF] Lepage | Molecular diversity of new Thermococcales isolates from a single area of hydrothermal deep-sea vents as revealed by randomly amplified polymorphic DNA fingerprinting and 16S rRNA gene sequence analysis[END_REF]. This can suggest that these strains use mobile genetic elements to share genetic information.

assembled
We wanted to form groups of closely related Thermococcus with strains we selected, so we used a phylogenetic tree to organize them, as well as all Thermococcales genomes available. To build a robust phylogenetic tree, we decided to employ the largest gene set shared by all organisms, thus only using genes in single copy. We conducted a pangenome analysis of all Thermococcales genomes available. This first pan-genome also allowed us to carry genus wide observations. In general for a pan-genomics study, the more genomes included, the smaller the core genome is. In contrast, the accessory genome increases in size (Tettelin et al., 2005;Touchon et al., 2009). Here the accessory genome seemed highly structured. We divided it in three. The first part was composed of 682 high frequency PCs. We supposed that this is likely due to the loss of these genes in a limited number of genomes. Then 2 437 PCs could be classified as medium-frequency within this pan-genome. In this case, it could be genes that were in the process of being lost from those genomes (Cordero and Polz, 2014). The largest part of this pangenome was composed by the PCs classified as low-frequency that looked like singletons. This could be attributed to a gene acquisition from horizontal transfer, or genes temporary present in genomes. In a previous Thermococcales comparative genomics study with 21 genomes, authors found 790 core genes, among them, 668 were present in single-copy [START_REF] Cossu | Comparative genomics reveals conserved positioning of essential genomic clusters in highly rearranged Thermococcales chromosomes[END_REF]. Compared to our results, 778 core genes and 602 SCGs, the addition of about 100 genomes did not significantly decrease the size of the core-genome. We have no reference concerning the accessory genome size.

While methods exist to provide universal set of genes to reconstruct a phylogeny [START_REF] Darling | PhyloSift: phylogenetic analysis of genomes and metagenomes[END_REF][START_REF] Rinke | Insights into the phylogeny and coding potential of microbial dark matter[END_REF][START_REF] Wu | A simple, fast, and accurate method of phylogenomic inference[END_REF], we decided to use SCGs from the 114 Thermococcales genomes available. Our SCGs set provided a richer collection with 602 genes chose without a priori. We also selected SCGs because working with universal genes sets presented the risk of having duplicated or absent genes from certain genomes. A surprising result from this phylogenomic analysis was that Thermococcus genus is not monophyletic. Indeed, the two Palaeococcus genomes were branched within the Thermococcus genus. The main difference between the two Thermococcus clades is the G+C content. The clade with the higher strain number had an average G+C content of 55%, whereas the other clade had an average G+C content of 41%. At the species level, the difference in G+C should be less than 3% [START_REF] Meier-Kolthoff | Taxonomic use of DNA G+C content and DNA-DNA hybridization in the genomic age[END_REF], but no thresholds are available for genus delineation. This Thermococcus low G+C clade either might represent a new genus or may be reclassified as

Palaeococcus. This should be the subject of a future study.

Then we investigated whether the difference of geographic origin, and therefore gene flow reduction or absence, can contribute to the formation of distinct monophyletic clades. Concerning group I, isolates were effectively clustered according to this criterion. Thermococcus isolates biogeographic clustering has already been investigated at small or larger scale. These studies showed a relationship between Thermococcus clones and the vent chemistry. It, also suggested the colonization of multiple ecological niches within the same hydrothermal vent (Huber et al., 2006;[START_REF] Lepage | Molecular diversity of new Thermococcales isolates from a single area of hydrothermal deep-sea vents as revealed by randomly amplified polymorphic DNA fingerprinting and 16S rRNA gene sequence analysis[END_REF]Price et al., 2015). Conversely, group II isolates did not follow a clustering pattern according to the geographic origin. This can suggest the presence of gene flow between EPR 9°N

and EPR 13°N hydrothermal sites.

Based on these results, we investigated the presence of microbial species within both groups. In other words, we tried to determine whether group I and group II represented species, populations, or multiple species? For each group, we used both ANI and DDH with thresholds 96% and 70% respectively. These metrics should delineate microbial species from genomic data (Auch et al., 2010a(Auch et al., , 2010b;;Konstantinidis and Tiedje, 2005;Rosselló-Mora, 2006;Stackebrandt et al., 2002). On group I isolates, 5 clusters were congruent with both methods, so we considered them as 5 species. to 100% within those groups, and around 96.5% between them. This may evoke the final phase of a speciation event. This was confirmed when looking at DDH results. They showed that the two latter clades were separated. However, one exception remained: T.

sp. IRI25c was above the threshold (DDH value equal to 70.1%), which supports the hypothesis that these two species are at the end of speciation process. Nevertheless, these two clades were each monophyletic in the phylogenetic tree. These combined results lead us to think that each clade is a species that seemed to diverge in a sympatric way, i.e., species that are present within the same environment. This suggests the presence of distinct ecological niches within DSHV chimneys colonized by closely related Thermococcales lineages harboring few distinct genes in relation to different ecological contrains.

Isolates of the group II represented 6 species based on both methods. To reinforce this result, all species corresponded to monophyletic clades. But here according to the SPC number found in each species that belong to group II, the species definition is too loose for clades we called Nautili-and Nautili-. Only and SPCs were found respectively, while , , and SPCs were found within Nautili-, Nautili-, Nautili-and Nautili-respectively. The high isolates number within the species could also explain this difference for Nautili-and Nautili-compared to the other.

Lastly, we indentified SPCs for each microbial species within each group. This was analyzed in order to learn more about selection pressures applied on these isolates. W did not take into account redundant functions from SPCs ( = functions that were also found on the rest of the pan-genome). What emerged from these unique functions is that the amino-acid metabolism seemed to be a major factor for differentiation between species. In group I, MC isolates remarkably harbored complete tryptophan and nearly complete histidine biosynthesis pathways, whereas AMTc isolates had symporters for alanine or glycine. )n the group )), Nautili-harbors the complete tryptophan biosynthesis pathway too. A recent transcriptomic study showed that within a piezophilic microorganism, the tryptophan biosynthesis was down regulated when the strain was cultivated at 25 MPa compared to atmospheric pressure (Amrani et al., 2014). This would mean that MC isolates, from shallow hot springs, can synthesize tryptophan while EXT12c and EXT13c isolates (Nautili-5) from deep-sea hydrothermal vents, can no longer synthesize this amino acid. This could be related to the higher energy cost of this pathway, no longer sustainable under hydrostatic pressure stress.

Moreover, in Pyrococcus, proteins from the piezophilic P. abyssi are composed of relatively fewer large amino acids, such as tryptophan or tyrosine, compared to proteins of the non-piezophilic P. furiosus. [START_REF] Di Giulio | A comparison of proteins from Pyrococcus furiosus and Pyrococcus abyssi: barophily in the physicochemical properties of amino acids and in the genetic code[END_REF]. This characteristic of proteins from piezophilic organisms could be verified in studied genomes by comparing the amino acid composition of SCGs.

Within all conspicuous SPCs identified in this study, 50 to 65% of PCs did not have annotations, whereas these genes are likely to have key roles in differentiation and adaptation between Thermococcus studied here. To study these unknown genes in more details, sequence similarity networks should be the next step to explore the presence of these PCs in other organisms (Atkinson et al., 2009;[START_REF] Meng | Analysis Of The Genomic Basis Of Functional Diversity In Dinoflagellates Using A Transcriptome-Based Sequence Similarity Network[END_REF]. In addition, phylogentic reconstruction of SPCs orthologous genes should also inform us about their origin, e.g. gene loss in other clades or aquisition through horizontal gene transfer.

5) Conclusion

From two sets of isolates belonging to Thermococcus, we built a phylogenomic tree based on core-gene present in single copy across all known genomes to date. From this tree, the genus Thermococcus was not monophyletic, and further studies are necessary to better delineate Thermococcales phylogeny.

Contrary to biogeographic studies on 16S rRNA gene and ITS sequences, isolates were not necessarily grouped according to their geographical origin, and surprisingly, one species may be present at several hydrothermal sites. This result was obtained with complete genome sequence of closely related organisms. From the SPCs highlighted as unique to the defined clades (species or location), these isolates are mainly differentiated based on amino acids metabolism, energy and carbohydrates metabolism genetic potentials. Despite the high level of unannotated proteins, it would be interesting to take their annotation further, using another approach such as similarity network.

To continue this work, it will be interesting to identify genomic context of these SPCs, to determine for example wether they are structured in operons or genomic islands, or whether they originate from horizontal transfers, and if it is the case, from which organism they acquired their genes.

6) Materials and Methods

For all isolates, genomic DNA was extracted as in the chapter Screening culture collection for Thermococcus . )llumina libraries were prepared using the kit TruSeq ® DNA PCR-free lib prep according to recommendation of the manufacturer, and 550 bp as insert size. Sequencing was performed at the Marine Biological Laboratory (Woods Hole, MA, USA), on an Illumina MiSeq system and MiSeq v3 reagent kit to get 300 bp paired-end reads.

Read quality was assessed with illumina-utils with the command iu-filter-qualityminoche [START_REF] Eren | A Filtering Method to Generate High Quality Short Reads Using Illumina Paired-End Technology[END_REF][START_REF] Minoche | Evaluation of genomic high-throughput sequencing data generated on Illumina HiSeq and Genome Analyzer systems[END_REF], and genome assembly was carried out with CLC Genomics Workbench v8.5.1

(https://www.qiagenbioinformatics.com/products/clc-genomics-workbench/), using size of k-mer ranging from 21 (default) to 63 (system limitation).

Pangenomics pipeline was carried out using anvi o v . . following the author s suggestion available here: http://merenlab.org/2016/11/08/pangenomics-v2/ [START_REF] Eren | Anvi'o: an advanced analysis and visualization platform for 'omics data[END_REF]. Briefly, we predict CDS with Prodigal v2.6.2, and annotate each CDS thanks to COG database through DIAMOND v0.9.8 [START_REF] Buchfink | Fast and sensitive protein alignment using DIAMOND[END_REF]Galperin et al., 2014;

III) In situ distribution of Thermococcales by a metapangenomics approach 1) Abstract

Thermococcales represent a hyperthermophilic archaeal order mainly found in hydrothermal vent environments. It may spread into the environment through marine currents and colonizes new hydrothermal systems. Its distribution is however of particular interest given its hyperthermophilic and strict anaerobic lifestyle limiting its dispersion by and survival in seawater. In this study, we wanted identify Thermococcales strains distribution in the environment by mapping published and available deep-sea hydrothermal vent and terrestrial hot spring metagenomes or metatranscriptomes on the Thermococcales genome collection established during thos work. From these mapping results, we detected more signals when metagenomes wrer obtained from a strain isolation site. We also identified two remarkable distribution patterns: either the genomes are found only in one single location, or they can be detected in several metagenomes of very diverse geographical origins. This is the case for example for Thermococcus cleftensis, which was detected in metagenomes from the Juan de Fuca Ridge and the Cayman Rise. In the future, with more metagenomes, this work will allows us to better indentify distribution of Thermococcales species, but also to give clues about the presence in the environment of less frequent strains such as ones of the Palaeococcus genus.

2) Introduction

Metagenomics is the study of DNA sequences found in the environment, without any a priori about the organism that owns this sequence. This tool revolutionized microbial ecology, with a tremendous amount of data available, but these data are harder to grasp owing to their complexity relative genomic data.

Deep-sea hydrothermal environments are also studied thanks to metagenomics. In this extreme environment, the archaeal order Thermococcales is widespread. These hyperthermophilic Archaea are among the first colonizers of newly formed hydrothermal chimney (McCliment et al., 2006;Nercessian et al., 2003;Pagé et al., 2008;Reysenbach et al., 2000b), they are detected within the first 4-5 days. They colonize walls of the chimney, where temperature is hot enough for their metabolism, but not too hot to kill them. In pure culture, the optimal growth temperature ranges from 75°C

to 105°C (Callac et al., 2016;Dalmasso et al., 2016a). In general, they grow better and faster under high hydrostatic pressure in lab conditions.

Thermococcales are widespread in deep-sea hydrothermal vents, thus we investigated sites where they can be present using metagenomes collected at both deep-sea hydrothermal vents and terrestrial hot springs, and all available Thermococcales genomes. With this framework, we aimed to visualize the dispersion of strains/isolates in the environment, and see if there were any dispersal barriers.

3) Results

In this chapter, we mapped 354 sets of environmental data, metagenomes and metatranscriptomes, from deep-sea hydrothermal vents, shallow hydrothermal vents and terrestrial hot springs (Appendix 2). These metagenomes were collected at For each genome, we looked for the percentage of detection of this genome across all metagenomes, or the proportion of a given genome that is covered at least 1X by mapped reads (Figure 28).

4) Discussion

In this short study, the aim was to track the presence of Thermococcales in different hydrothermal places. Metagenomes and metatranscriptomes derived mainly from the North Pacific at Juan De Fuca ridge (Fortunato and Huber, 2016), and this might decrease the number of genomes detected, because many isolates with sequenced genomes come from other places like the Atlantic Ocean.

In metagenomes, no Thermococcales was detected, like at Loki s Castle, or at Lost City (LostCityMAR), whereas they were present according to studies based on the 16S rRNA genes [START_REF] Brazelton | Methaneand Sulfur-Metabolizing Microbial Communities Dominate the Lost City Hydrothermal Field Ecosystem[END_REF]Jaeschke et al., 2012).

A parameter that we did not take into account here is the quantity of reads per metagenomes. We did not perform any normalization on the quantity of reads. This may add biases, because the more data there are in a metagenome, the greater is the chance of having detected genomes. This could explain why we detect traces of genomes (less than 0.001%) within terrestrial hot springs.

From this plot, it seems that some Thermococcales are widespread, while other only live in a unique place, like the Palaeococcus used here. This could explain why this genus is under-represented among Thermococcales isolates. But this Palaeococcus pacificus was characterized from the EPR 1°S hydrothermal vent [START_REF] Zeng | Palaeococcus pacificus sp. nov., an archaeon from deep-sea hydrothermal sediment[END_REF], suggesting the presence of Palaeococcus isolates in JdF. Moreover, one 16S rRNA gene sequence and ITS belonging to Palaeococcus was found in Axial Seamount from JdF (accession: AY559124), indicating their presence at this geographic location.

In samples from the Cayman trench, detection shed light on two genomes: T. piezophilus and T. paralvinellae. The first one was isolated from this place (site Piccard), while the second was isolated from a sample from JdF Endeavour (Dalmasso et al., 2016a;Hensley et al., 2014). This tends to indicate that this strain might be able of moving over long distances, or that close isolates are present in these locations.

This archaeal order of Thermococcales acts as one of the first colonizers in newly formed hydrothermal vents (McCliment et al., 2006;Nercessian et al., 2003;Pagé et al., 2008;[START_REF] Reysenbach | Novel Bacterial and Archaeal Lineages from an In Situ Growth Chamber Deployed at a Mid-Atlantic Ridge Hydrothermal Vent[END_REF]. A hypothesis on how they colonize is that they disseminate in the environment through oceanic currents and they reach a new site randomly [START_REF] Wirth | Colonization of Black Smokers by Hyperthermophilic Microorganisms[END_REF].

5) Conclusion

In this exploratory study, we aimed at tracking the presence of known Thermococcales in different geographical places. Despite the low detection of genomes, broad outlines emerged. These isolates are not present within terrestrial hot spring, certainly by the lack of a link between them and deep-sea environments. It is also likely that at temporal dynamics exists, as Thermococcales are not present at the same rate over the years. In some places, the diversity of Thermococcales is high, like in Menez Gwen (MenezGwenMAR), whereas other metagenomes did not captured sequences affiliated to Thermococcales. To finish, this work brings us clues on places where to search for new strains, like for Palaeococcus that seems to be present in the hydrothermal site Dependable at the Juan de Fuca ridge, whereas no isolates was characterized from this location.

6) Materials and Methods

Metagenomes and metatranscriptomes were recovered with SRAtoolkit v2.8.2: we downloaded raw data using the prefetch command with the SRA id or each metagenome as argument. Then we used fastq-dump with the parameter --split-files to convert raw file to two FastQ files (one file for each paired-end reads). Then each data set went through quality control with illumina-utils and command iu-filter-quality-minoche [START_REF] Eren | A Filtering Method to Generate High Quality Short Reads Using Illumina Paired-End Technology[END_REF][START_REF] Minoche | Evaluation of genomic high-throughput sequencing data generated on Illumina HiSeq and Genome Analyzer systems[END_REF]. Metagenomes and metatranscriptomes were mapped onto genomes with bowtie2 v2.2.9, default parameters (Langmead and Salzberg, 2012).

Anvi o was used to merge all mapping results, following profiling and merging parts of the tutorial available here: http://merenlab.org/2016/06/22/anvio-tutorial-v2/ [START_REF] Eren | Anvi'o: an advanced analysis and visualization platform for 'omics data[END_REF]. The data matrix about genomes detection was recovered from the command anvi-summarize. To obtain the figure presented in this chapter, we used the command anvi-interactive, with the transposed genomes detection matrix and a custom cladogram that grouped together all replicates for a metagenome.

V) Published data

During this project, 48 genomes were sequenced, some of which probably represent new species of Thermococcus. We published the genome of Thermococcus sp. EXT12c, isolated from a deep-sea hydrothermal vent rock sample at the EPR 9°N. Its closest relative is T. nautili, but the low DNA similarity values (ANI and DDH) with known strains strongly suggest that this isolate represents a new species. In comparative genomics study, it appeared in SPCs that this isolate had the complete biosynthesis pathway for tryptophan, an energy costly amino-acid synthesis pathway absent in several piezophilic microorganisms. Up to date, it was shown in a piezophilic bacterium that the synthesis of this amino acid is greatly reduced when the bacterium is cultivated under high hydrostatic pressure (Amrani et al., 2014). Concerning Archaea, a transcriptomics analysis carried out in T. barophilus and T. kodakaraensis revealed only a slight difference of expression for a few genes involved in this biosynthesis pathway. It would be interesting to explore this feature by transcriptomics analysis over a range of hydrostatic pressure culture conditions using a method with high sequencing depth.

General synthesis

This research has been designed to study the ecology of microorganisms in deep environments using high throughput approaches such as complete genome sequencing, metagenomics, and metatranscriptomics. In this ecogenomics framework, I have been interested in the genomic diversity of closely related Thermococcus isolates. They are defined as closely related based on a phylogenetic point of view. We wanted to explore hypotheses about the mechanisms that influence the diversification of these genomes, and also learn more about the selection pressures that such organisms with restricted ecological niches can face in deep-sea hydrothermal environments.

The first phase of this work was to use the culture collection available in the laboratory, UBOCC. The marine part of the collection consists of approximately 1,300 isolates collected from various marine samples collected over the years during oceanographic cruises. Of these isolates, about 300 were annotated as belonging to the Thermococcales order. This order is composed of hyperthermophilic Archaea mainly found in deep marine hydrothermal vents. This assignment was based on morphological and cultural criteria, i.e. isolates that grow in anaerobic conditions at a temperature of about 85°C, on a medium rich in organic matter, mobile and having a coccoid morphology. In order to confirm and refine this first assignment, we used a ubiquitous marker: the gene coding for the small ribosome subunit RNA, i.e. 16S rRNA. This marker, once sequenced, was used to construct a phylogenetic tree to infer taxonomic affiliation at the genus level. All isolates were cultured and incubated at 80 or 85°C for 16 to 18 hours. Then the DNA of each isolate was extracted and we amplified by PCR the sequence of the gene coding for 16S rRNA, as well as the sequence between 16S-23S rRNA genes, called

Internal Transcribed Spacer (ITS). The interest of sequencing the ITS is to have an additional marker to build a more robust phylogenetic tree. In total, for each isolate, 3 sequencings according to the Sanger method were required to obtain the complete sequence of each "16S-ITS". The sequences were assembled and their quality checked. A total of 273 sequences were completed and suitable to proceed to the next stage of phylogenetic tree construction. Sequences of 16S-ITS from the representatives of the three Thermococcales genera (Pyrococcus, Thermococcus, and Palaeococcus) were downloaded from the public databases. These and the 273 sequences obtained during this work were aligned and a tree was constructed. Figure 20 shows a simplified version of this tree. Of the 273 isolates, 14 were classified as belonging to the genus Pyrococcus and the remaining 259 were affiliated to Thermococcus (Appendix 1). Finally, from this tree, two groups of genomes were selected according to the following criteria: (i) several geographical origins, (ii) several genomes for the same geographical origin, (iii) monophyletic group if possible. Following these criteria, the first selected group included 21 isolates from the East Pacific Ridge 13°N (EPR 13°N), the Rainbow hydrothermal field located on the Mid-Atlantic Ridge, and Saint-Paul Island located in South Indian Ocean (Figure 21). The second group contained 27 genomes close to Thermococcus nautili, which originated from EPR 9°N and EPR 13°N in the Pacific Ocean (Figure 21).

The second part of my thesis began with the sequencing of the 48 genomes selected. All DNA samples were extracted at the LM2E. Half of the genomes were sent directly to the Marine Biological Laboratory (MBL) in Woods Hole, USA, for sequencing. For the second half of the genomes, the Illumina sequencing libraries were prepared at the LM2E and sent to the MBL for sequencing. We have chosen to sequence on Illumina MiSeq in pair end 2x300 bp. I then assembled all genomes using CLC Genomics Workbench, using different sizes of k-mer. A total of 46 genomes were successfully assembled, of which 19

were successfully assembled within a single circular contig, 15 within a non-circularized contig and 13 genomes remained fragmented (2-57 contigs). Sequencing failed for a group I genome (MC5), and it appeared that the genome of Thermococcus sp.

E15P25 (Group II) was contaminated, two genomes seeming to be present, making its use impossible.

In a second phase, we built a phylogenomic tree to put all these genomes within an evolutionary context. The phylogeny realized was based on the single-copy coregenome genes, because it is a rich data set defined without a priori on the genes function. To obtain this gene set, it was necessary to carry out a pangenomics analysis, which made it possible to define on the one hand, all the genes shared by all the genomes studied (= core-genome) and on the other hand, all the other genes, i.e. the accessory genome. The union of these two categories formed the pangenome. The latter was established with anvi'o. Briefly, we identified coding sequences (CDS) in all genomes and then compared all the sequences. This result was then provided to MCL, an algorithm that aggregates genes via a graph approach. A list of clusters of genes (PC, Protein Clusters) emerged. In a PC, if there was a gene of each genome, that PC belonged to the core-genome. When a PC in the core genome contained a unique gene from each of the genomes, this PC belonged to the "single copy core-gene (SCGs) genes". All noncore PCs were attributed to the accessory genome. Figure 23 shows a representation of this pangenome and the distribution of accessory PCs. After this step, the 602 SCGs were extracted, aligned, trimmed and concatenated. This alignment of approximately 92,000 non-redundant positions has been used to construct the phylogeny of these 114 genomes, using the maximum likelihood method (Figure 24A). In this tree, the 21 isolates of Group I formed a monophyletic clade. Two genomes from the public databases were added to this group: Thermococcus celericrescens and T. sp. 4557. Group II was composed of 34 genomes: 25 sequenced in this project, 1 reference genome (T.

nautili) and 8 unpublished genomes provided by the MBGE laboratory (Pasteur Institute). This group was supposed to contain 26 of the isolates sequenced during this work, but the strain T. sp. IRI06c was branched elsewhere in the tree. After verification, the 16S rRNA gene sequence in the genome and the sequence obtained in the first part of the thesis differed by 15 nucleotides indicating that it was not the same isolate. This genome was therefore simply retained for the global pangenome, but was not used for the rest of this work.

As this tree confirms the existence of these two distinct groups, we questioned the nature of the parameters that could explain the organization of isolates in each group.

Initially, the impact of geographical origin was analyzed. For group I, this factor alone explained the organization of these genomes in clades (group with a common ancestor) in this tree (Figure 24B). The genomes of group II did not follow this trend, as the geographical origin did not explain their organization in this tree. The second parameter studied was the presence of microbial species via the two metrics ANI (average nucleotide identity between genomes) and DNA hybridization (DDH). Group I was composed of 7 species according to these two metrics: one species for each geographic origin, except for the Rainbow site, which had 3 sympatric species (Figure 25). Group II was composed of 6 species, always according to the ANI and the DDH (Figure 25).

The final step in this study was to identify genes and metabolic pathways involved in these differentiation processes. For each group, a new genome was established . From there, the focus was then on identifying genes specific to each species and identifying functions found only in those genes. In summary, there were a very variable number of specific genes, from 1 to 336 depending on the species. About half had no annotation, and of the remaining genes, many functions were redundant between species. Nevertheless, the specific functions were still interesting. They were mainly associated with amino acid metabolism, energy metabolism, carbohydrate metabolism or the transport of inorganic ions. All of this has provided us information on the selection pressures that can be applied to these microorganisms in deep environments.

This has also informed us about the metabolisms acquired or lost that lead to the formation of new microbial species in the deep marine hydrothermal environment.

The last part of this thesis was about the distribution of Thermococcales in the environment. To do this, metagenomes and metatranscriptomes from deep hydrothermal environments and terrestrial hot springs were mapped onto Thermococcales genomes (Figure 28). Overall, genomes were found in the seabed metagenomes but not in those from terrestrial hot springs, the barrier between these two environments being probably too complex to cross simply because of chance and marine streams. Unlike Thermococcus, Pyrococcus and Palaeococcus genera were much less detected in metagenomes. This suggests that these Archaea inhabit more restricted and low abundant ecological niches in the environment. Finally, some Thermococcus strains, such as T. cleftensis, appeared to be present in several locations (Northeast Pacific Ocean and Cayman Trough in the Atlantic Ocean), suggesting that they would be able to migrate over long distances, while other strains appear to remain at only one place. The novelty of the latter study was to provide clues to isolate interesting new taxa, such as Palaeococcus, which are poorly represented compared to the vast majority of isolated, characterized and sequenced Thermococcus.

Conclusion

In conclusion, during these three years of work, several aspects of the microbial ecology were covered. The first step of this work was to classify uncharacterized isolates from our culture collection to select closely related isolates of Thermococcus originating from different locations. These isolates were investigated in great details in the second part of the work. Here, comparative genomics allowed us to highlight mechanisms and genes resulting from early stages of genome differentiation. The objective of the last part of the thesis was to identify the presence of genomes in environmental metagenomes, and thereby to focus on their biogeography.

The first part of the work required a year and a half to select and sequence the 48 genomes of isolates from the culture of all UBOCC isolates. This involved re-culturing and DNA extraction for all isolates. Then, the tools available to make assembly of read Sanger reads can easily take into account two sequences (1F / 1R). But I could not find any tools able to assemble 3 reads (1F / 2R). Therefore, this step was done manually, as well as quality control. Finally, many tree-building methods were tested before reaching our final result. Although it took a long time, this initial work was necessary to know the phylogenetic diversity of the isolates in our possession.

Several results emerge from comparative genomics. First of all, it would seem that the phylogeny of Thermococcales needs to be revised. The genus Thermococcus does not constitute a monophyletic group in the phylogenomic tree. Further consideration should be given to this subject, using other approaches and taxonomic markers. Second, with regard to the genomic diversity of the two groups of isolates studied, geographical isolation may explain the differentiation of genomes for one group. Concerning the second group, isolates are not organized according to this parameter. The colonization of different ecological niches might explain their evolutionary history. Among these groups, several species are probably present. The characterization of their phenotypes will be necessary to confirm it as the species definition of prokaryotic is based on phylophenetic features. The analysis of their specific genes revealed several metabolisms involved in the differentiation of genomes, including amino acid metabolism and energy production metabolism. Many functions are still unknown. In these gene pools, there are probably interesting functions. Further analysis using similarity networks can shed light on these functions.

The last section of the manuscript remains to be investigated in greater details, in particular by bringing new metagenomes. This new approach as the benefit to provide clues to target geographic areas where new close phylotypes of a reference strain may be present. (1976) Les perspectives sont nombreuses: Ø Identification des fonctions métaboliques des groupes de protéines spécifiques pour chaque souche Ø Mise en relation de la présence de gènes spécifiques chez une souche issue d'un site hydrothermal et de son rôle égologique associé Ø Reconstruction de l'histoire évolutive de ces souches grâce à plusieurs jeux de données (protéines ribosomales, gènes en copie unique, etc.)

Références

Les Archées et les Bactéries sont les êtres vivants parmi les plus abondants sur Terre. Ces organismes sont présents partout: dans les sols, dans les eaux, en symbiose avec des animaux ou des végétaux, etc. Les cheminées hydrothermales profondes (Figure 1) combinent des conditions extrêmes de haute température et de haute pression. Ces édifices profonds sont colonisées par de nombreux microorganismes extrêmophiles dont la résistance à ces conditions en fait des modèles particulièrement intéressants pour l'étude des mécanismes d'adaptation. L'objectif de ma thèse consiste à explorer la diversité génomique du genre Thermococcus, une archée hyperthermophile habituellement présente sur ces édifices hydrothermaux profonds (Figure 2). Lors de ce projet, 48 isolats de Thermococcus ont été séquencés, ils appartiennent à deux populations distinctes. La première, proche de l'espèce Thermococcus nautili, comprend 27 isolats provenant des océans Atlantique et Pacifique (Figure 3). La seconde population est proche de l'espèce Thermococcus sp. 4557 et compte 21 isolats. Actuellement, les génomes de 45 d'entre elles ont été séquencés et assemblés. Les résultats exposés ici sont préliminaires et portent sur 23 souches appartenant à la population 'Thermococcus nautili '. Les isolats de cette population se trouvent être particulièrement proches. Ceci est visible sur l'arbre phylogénétique construit avec le marqueur ARNr 16S (Figure 4). Cette multitude d'origines est intéressante car chaque site hydrothermal est unique (géochimie, géographie). Or, si plusieurs isolats se révèlent être proches sur le plan génomique, mais proviennent de différents sites hydrothermaux, il y a une forte présomption d'adaptation de leur patrimoine génétique à leurs environnements respectifs. Les génomes ont été annotés en utilisant Anvi'o (Eren et al., 2006). La figure 5 représente les groupes de protéines propre à une souche de même que ceux partagés.

La seconde partie de ma thèse a débuté par le séquençage des 48 génomes sélectionnés. The! immense! genomic! diversity! of! microorganisms! allows! them! to! live! everywhere,! even! in! extreme! environments! such! as! deep! hydrothermal! vents.! Scattered! over! the! seabed,! these! are! a! good! model! for! studying! the! biogeography! and! genomes! diversification.! A! comparative! genomics! approach!has!been!used!on!closely!related!isolates,!of!the!genus!Thermococcus.!This!work!aimed!at! identifying!mechanisms!that!have!a!role!in!the!diversification!of!these!genomes,!and!also!to!identify! genes! involved! in! this! differentiation.! For! this! purpose,! two! groups! of! about! 20! isolates! with! different!geographical!origins!were!selected!and!sequenced.! The!geographical!isolation!resulting!from!colonization!of!new!hydrothermal!systems!is!likely!to!be! a!diversification!and!speciation!factor!for!some!isolates.!But!when!hydrothermal!sites!are!relatively! close,!it!would!seem!that!gene!transfer!between!isolates!is!still!possible.!In!this!case,!adaptation!to! new! ecological! niches! would! be! a! factor! contributing! to! the! genomes! diversification.! The! comparative! genomics! approach! allowed! highlighting! genes! specific! to! certain! subgroups,! related! to! species.! These! genes! are! involved! in! amino! acid! metabolism,! energy! production! and! the! transport!of!inorganic!ions.!This!reflects!selection!pressures!that!these!organisms!may!experience! in!these!environments,!otherwise!hostile!to!many!forms!of!life.! ! Key!words:!Comparative!genomics,!Thermococcus,!Diversification,!Genome,!Hyperthermophile! !

Figure 1 :

 1 Figure 1: Localization of known hydrothermal vents...................................................................... Figure 2: Formation of a deep-sea hydrothermal vent ................................................................... Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin.....Figure 4: Optimal growth temperature of microorganisms .......................................................... Figure 5: Phylogenetic tree relating the archaeal domain ........................................................... Figure 6: Representation of the ranks in the modern classification ........................................ Figure 7: General principle of DNA-DNA hybridization. ...............................................................Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. .................................................................................................................................................... Figure 9: Illustration of the stable ecotype model .......................................................................... Figure 10: Emergence of 2 populations .............................................................................................. Figure 11: General tools used for Thermococcales cultivation ...................................................Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers .................................................... Figure 13: PCR template used to amplified the 16S-ITS DNA sequence ................................ Figure 14: Migration profile of the DNA ladder employed during electrophoresis ........... Figure 15: Overview of the Sanger sequencing framework ........................................................Figure 16: Covaris ® and Bioanalyzer instruments ......................................................................... Figure 17: General principle of Illumina sequencing .....................................................................Figure 18: Example of an electropherogram ..................................................................................... Figure 19: Example of Illumina ® read quality ..................................................................................Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates ............................................................................................................................................................................. Figure 21: Geographic origins of isolates selected for whole genome sequencing ............ Figure 22: Examples of normal vs. potential mobile genetic elements coverages ............. Figure 23: Pangenomics analysis of 114 Thermococcales genomes ........................................ Figure 24: Phylogenomic tree of Thermococcales genomes ........................................................ Figure 25: Genomic similarity of isolates from groups I and II .................................................. Figure 26: Group I pan-genome overview .........................................................................................Figure 27: Group II pan-genome overview ........................................................................................Figure 28: Mapping of metagenomes on Thermococcales genomes .....................................

Figure 4 :

 4 Figure 1: Localization of known hydrothermal vents...................................................................... Figure 2: Formation of a deep-sea hydrothermal vent ................................................................... Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin.....Figure 4: Optimal growth temperature of microorganisms .......................................................... Figure 5: Phylogenetic tree relating the archaeal domain ........................................................... Figure 6: Representation of the ranks in the modern classification ........................................ Figure 7: General principle of DNA-DNA hybridization. ...............................................................Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. .................................................................................................................................................... Figure 9: Illustration of the stable ecotype model .......................................................................... Figure 10: Emergence of 2 populations .............................................................................................. Figure 11: General tools used for Thermococcales cultivation ...................................................Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers .................................................... Figure 13: PCR template used to amplified the 16S-ITS DNA sequence ................................ Figure 14: Migration profile of the DNA ladder employed during electrophoresis ........... Figure 15: Overview of the Sanger sequencing framework ........................................................Figure 16: Covaris ® and Bioanalyzer instruments ......................................................................... Figure 17: General principle of Illumina sequencing .....................................................................Figure 18: Example of an electropherogram ..................................................................................... Figure 19: Example of Illumina ® read quality ..................................................................................Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates ............................................................................................................................................................................. Figure 21: Geographic origins of isolates selected for whole genome sequencing ............ Figure 22: Examples of normal vs. potential mobile genetic elements coverages ............. Figure 23: Pangenomics analysis of 114 Thermococcales genomes ........................................ Figure 24: Phylogenomic tree of Thermococcales genomes ........................................................ Figure 25: Genomic similarity of isolates from groups I and II .................................................. Figure 26: Group I pan-genome overview .........................................................................................Figure 27: Group II pan-genome overview ........................................................................................Figure 28: Mapping of metagenomes on Thermococcales genomes .....................................

Figure 5 :

 5 Figure 1: Localization of known hydrothermal vents...................................................................... Figure 2: Formation of a deep-sea hydrothermal vent ................................................................... Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin.....Figure 4: Optimal growth temperature of microorganisms .......................................................... Figure 5: Phylogenetic tree relating the archaeal domain ........................................................... Figure 6: Representation of the ranks in the modern classification ........................................ Figure 7: General principle of DNA-DNA hybridization. ...............................................................Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. .................................................................................................................................................... Figure 9: Illustration of the stable ecotype model .......................................................................... Figure 10: Emergence of 2 populations .............................................................................................. Figure 11: General tools used for Thermococcales cultivation ...................................................Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers .................................................... Figure 13: PCR template used to amplified the 16S-ITS DNA sequence ................................ Figure 14: Migration profile of the DNA ladder employed during electrophoresis ........... Figure 15: Overview of the Sanger sequencing framework ........................................................Figure 16: Covaris ® and Bioanalyzer instruments ......................................................................... Figure 17: General principle of Illumina sequencing .....................................................................Figure 18: Example of an electropherogram ..................................................................................... Figure 19: Example of Illumina ® read quality ..................................................................................Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates ............................................................................................................................................................................. Figure 21: Geographic origins of isolates selected for whole genome sequencing ............ Figure 22: Examples of normal vs. potential mobile genetic elements coverages ............. Figure 23: Pangenomics analysis of 114 Thermococcales genomes ........................................ Figure 24: Phylogenomic tree of Thermococcales genomes ........................................................ Figure 25: Genomic similarity of isolates from groups I and II .................................................. Figure 26: Group I pan-genome overview .........................................................................................Figure 27: Group II pan-genome overview ........................................................................................Figure 28: Mapping of metagenomes on Thermococcales genomes .....................................

Figure 8 :

 8 Figure 1: Localization of known hydrothermal vents...................................................................... Figure 2: Formation of a deep-sea hydrothermal vent ................................................................... Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin.....Figure 4: Optimal growth temperature of microorganisms .......................................................... Figure 5: Phylogenetic tree relating the archaeal domain ........................................................... Figure 6: Representation of the ranks in the modern classification ........................................ Figure 7: General principle of DNA-DNA hybridization. ...............................................................Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. .................................................................................................................................................... Figure 9: Illustration of the stable ecotype model .......................................................................... Figure 10: Emergence of 2 populations .............................................................................................. Figure 11: General tools used for Thermococcales cultivation ...................................................Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers .................................................... Figure 13: PCR template used to amplified the 16S-ITS DNA sequence ................................ Figure 14: Migration profile of the DNA ladder employed during electrophoresis ........... Figure 15: Overview of the Sanger sequencing framework ........................................................Figure 16: Covaris ® and Bioanalyzer instruments ......................................................................... Figure 17: General principle of Illumina sequencing .....................................................................Figure 18: Example of an electropherogram ..................................................................................... Figure 19: Example of Illumina ® read quality ..................................................................................Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates ............................................................................................................................................................................. Figure 21: Geographic origins of isolates selected for whole genome sequencing ............ Figure 22: Examples of normal vs. potential mobile genetic elements coverages ............. Figure 23: Pangenomics analysis of 114 Thermococcales genomes ........................................ Figure 24: Phylogenomic tree of Thermococcales genomes ........................................................ Figure 25: Genomic similarity of isolates from groups I and II .................................................. Figure 26: Group I pan-genome overview .........................................................................................Figure 27: Group II pan-genome overview ........................................................................................Figure 28: Mapping of metagenomes on Thermococcales genomes .....................................

Figure 12 :

 12 Figure 1: Localization of known hydrothermal vents...................................................................... Figure 2: Formation of a deep-sea hydrothermal vent ................................................................... Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin.....Figure 4: Optimal growth temperature of microorganisms .......................................................... Figure 5: Phylogenetic tree relating the archaeal domain ........................................................... Figure 6: Representation of the ranks in the modern classification ........................................ Figure 7: General principle of DNA-DNA hybridization. ...............................................................Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. .................................................................................................................................................... Figure 9: Illustration of the stable ecotype model .......................................................................... Figure 10: Emergence of 2 populations .............................................................................................. Figure 11: General tools used for Thermococcales cultivation ...................................................Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers .................................................... Figure 13: PCR template used to amplified the 16S-ITS DNA sequence ................................ Figure 14: Migration profile of the DNA ladder employed during electrophoresis ........... Figure 15: Overview of the Sanger sequencing framework ........................................................Figure 16: Covaris ® and Bioanalyzer instruments ......................................................................... Figure 17: General principle of Illumina sequencing .....................................................................Figure 18: Example of an electropherogram ..................................................................................... Figure 19: Example of Illumina ® read quality ..................................................................................Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates ............................................................................................................................................................................. Figure 21: Geographic origins of isolates selected for whole genome sequencing ............ Figure 22: Examples of normal vs. potential mobile genetic elements coverages ............. Figure 23: Pangenomics analysis of 114 Thermococcales genomes ........................................ Figure 24: Phylogenomic tree of Thermococcales genomes ........................................................ Figure 25: Genomic similarity of isolates from groups I and II .................................................. Figure 26: Group I pan-genome overview .........................................................................................Figure 27: Group II pan-genome overview ........................................................................................Figure 28: Mapping of metagenomes on Thermococcales genomes .....................................

Figure 16 :

 16 Figure 1: Localization of known hydrothermal vents...................................................................... Figure 2: Formation of a deep-sea hydrothermal vent ................................................................... Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin.....Figure 4: Optimal growth temperature of microorganisms .......................................................... Figure 5: Phylogenetic tree relating the archaeal domain ........................................................... Figure 6: Representation of the ranks in the modern classification ........................................ Figure 7: General principle of DNA-DNA hybridization. ...............................................................Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. .................................................................................................................................................... Figure 9: Illustration of the stable ecotype model .......................................................................... Figure 10: Emergence of 2 populations .............................................................................................. Figure 11: General tools used for Thermococcales cultivation ...................................................Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers .................................................... Figure 13: PCR template used to amplified the 16S-ITS DNA sequence ................................ Figure 14: Migration profile of the DNA ladder employed during electrophoresis ........... Figure 15: Overview of the Sanger sequencing framework ........................................................Figure 16: Covaris ® and Bioanalyzer instruments ......................................................................... Figure 17: General principle of Illumina sequencing .....................................................................Figure 18: Example of an electropherogram ..................................................................................... Figure 19: Example of Illumina ® read quality ..................................................................................Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates ............................................................................................................................................................................. Figure 21: Geographic origins of isolates selected for whole genome sequencing ............ Figure 22: Examples of normal vs. potential mobile genetic elements coverages ............. Figure 23: Pangenomics analysis of 114 Thermococcales genomes ........................................ Figure 24: Phylogenomic tree of Thermococcales genomes ........................................................ Figure 25: Genomic similarity of isolates from groups I and II .................................................. Figure 26: Group I pan-genome overview .........................................................................................Figure 27: Group II pan-genome overview ........................................................................................Figure 28: Mapping of metagenomes on Thermococcales genomes .....................................

Figure 18 :

 18 Figure 1: Localization of known hydrothermal vents...................................................................... Figure 2: Formation of a deep-sea hydrothermal vent ................................................................... Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin.....Figure 4: Optimal growth temperature of microorganisms .......................................................... Figure 5: Phylogenetic tree relating the archaeal domain ........................................................... Figure 6: Representation of the ranks in the modern classification ........................................ Figure 7: General principle of DNA-DNA hybridization. ...............................................................Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. .................................................................................................................................................... Figure 9: Illustration of the stable ecotype model .......................................................................... Figure 10: Emergence of 2 populations .............................................................................................. Figure 11: General tools used for Thermococcales cultivation ...................................................Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers .................................................... Figure 13: PCR template used to amplified the 16S-ITS DNA sequence ................................ Figure 14: Migration profile of the DNA ladder employed during electrophoresis ........... Figure 15: Overview of the Sanger sequencing framework ........................................................Figure 16: Covaris ® and Bioanalyzer instruments ......................................................................... Figure 17: General principle of Illumina sequencing .....................................................................Figure 18: Example of an electropherogram ..................................................................................... Figure 19: Example of Illumina ® read quality ..................................................................................Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates ............................................................................................................................................................................. Figure 21: Geographic origins of isolates selected for whole genome sequencing ............ Figure 22: Examples of normal vs. potential mobile genetic elements coverages ............. Figure 23: Pangenomics analysis of 114 Thermococcales genomes ........................................ Figure 24: Phylogenomic tree of Thermococcales genomes ........................................................ Figure 25: Genomic similarity of isolates from groups I and II .................................................. Figure 26: Group I pan-genome overview .........................................................................................Figure 27: Group II pan-genome overview ........................................................................................Figure 28: Mapping of metagenomes on Thermococcales genomes .....................................

Figure 20 :

 20 Figure 1: Localization of known hydrothermal vents...................................................................... Figure 2: Formation of a deep-sea hydrothermal vent ................................................................... Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin.....Figure 4: Optimal growth temperature of microorganisms .......................................................... Figure 5: Phylogenetic tree relating the archaeal domain ........................................................... Figure 6: Representation of the ranks in the modern classification ........................................ Figure 7: General principle of DNA-DNA hybridization. ...............................................................Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. .................................................................................................................................................... Figure 9: Illustration of the stable ecotype model .......................................................................... Figure 10: Emergence of 2 populations .............................................................................................. Figure 11: General tools used for Thermococcales cultivation ...................................................Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers .................................................... Figure 13: PCR template used to amplified the 16S-ITS DNA sequence ................................ Figure 14: Migration profile of the DNA ladder employed during electrophoresis ........... Figure 15: Overview of the Sanger sequencing framework ........................................................Figure 16: Covaris ® and Bioanalyzer instruments ......................................................................... Figure 17: General principle of Illumina sequencing .....................................................................Figure 18: Example of an electropherogram ..................................................................................... Figure 19: Example of Illumina ® read quality ..................................................................................Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates ............................................................................................................................................................................. Figure 21: Geographic origins of isolates selected for whole genome sequencing ............ Figure 22: Examples of normal vs. potential mobile genetic elements coverages ............. Figure 23: Pangenomics analysis of 114 Thermococcales genomes ........................................ Figure 24: Phylogenomic tree of Thermococcales genomes ........................................................ Figure 25: Genomic similarity of isolates from groups I and II .................................................. Figure 26: Group I pan-genome overview .........................................................................................Figure 27: Group II pan-genome overview ........................................................................................Figure 28: Mapping of metagenomes on Thermococcales genomes .....................................

  genomes ........................................................................................................................................................... Table

  Speciation stages under different conditions of selections and homologous recombination ............................................................................................................................................... Table 5: Summary of genomes sequenced in this study ............................................................... Table 6: Summary of other genomes used in pangenomics study............................................ Table 7: Specific protein clusters and classification of specific functions .............................

Figure 1 :Figure 2 :

 12 Figure 1: Localization of known hydrothermal vents From http://www.whoi.edu/page.do?pid=83497&tid=7842&cid=71854

Figure 3 :

 3 Figure 3: Bacterial diversity of hydrothermal active sediments of the Guaymas Basin These distance trees are based on full size 16S rRNA gene sequences. Left tree: Bacteria without phylum of Proteobacteria. Right tree: Proteobacteria only. From Teske et al., 2002.

Figure 4 :

 4 Figure 4: Optimal growth temperature of microorganisms From Madigan et al., 2012

Figure 5 :

 5 Figure 5: Phylogenetic tree relating the archaeal domain Phylogenetic tree from[START_REF] Adam | The growing tree of Archaea: new perspectives on their diversity, evolution and ecology[END_REF]. Red dots represent different root for this tree. The #1 represent the traditional root[START_REF] Woese | Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya[END_REF], between Euryarchaeota and Crenarchaeota (now TACK). The #2 represents a new well-supported root proposed byRaymann et al (2015). Grey names represent clades for which no isolates are available. Bottom right panel shows a simplified archaeal phylogeny, from Castelle and Banfield 2018. SC: Super Class; P: Phylum; SP: Super Phylum.

Figure 6 :

 6 Figure 6: Representation of the ranks in the modern classification

Figure 7 :

 7 Figure 7: General principle of DNA-DNA hybridization. Black strands represent DNA of the reference strain. Red strands represent DNA of the tested isolate. In the last step, homoduplex are displayed as two strands of the same color (black or red), while heteroduplex are displayed as a mixture of black and red strands. (From Rosselló-Mora and Amann, 2001).

Figure 8 :

 8 Figure 8: Relation between 16S rRNA gene sequence similarity and DNA-DNA relatedness. The red horizontal bar indicates the old 97% similarity threshold. The blue horizontal bar relates the new threshold (98.7-99% similarity). And the green vertical bar figure the 70% DNA-DNA reassociation threshold. From Stackebrandt and Ebers, 2006.

Figure 9 :

 9 Figure 9: Illustration of the stable ecotype model This model depicts differentiation of bacterial/archaeal population under the stable ecotype model. Asterisks represent selection events (genome-wide selective sweep)that purge almost all diversity (shown as dashed lines) that has arisen since the last selection event. from[START_REF] Cohan | A Systematics for Discovering the Fundamental Units of Bacterial Diversity[END_REF] Fraser et al., 2009.

Figure 10 :

 10 Figure 10: Emergence of 2 populations Thin purple and black arrows represent genes exchange between members. Big green and red arrows represent the acquisition of an adaptive allele (Adapted fromShapiro et al., 2012)

Figure 11 :

 11 Figure 11: General tools used for Thermococcales cultivation A: a vial used for anaerobic culture; B: Optic microscope for magnificence x400 and x1000; C: Cord -Ruwisch test, illustration of the precipitation of H2S into CuS. From left to right: Culture producing decreased quantity of H2S, and negative control (fresh medium).

Figure 12 :

 12 Figure 12: NanoDrop ® ND1000 and Quantus ® fluorometers NanoDrop ® ND1000 is presented on the left side, and Quantus ® on the right side

  reagents (primers and qPCR Master Mix) were added into each well of the qPCR plate. The thermal cycler used was a StepOne™ apparatus Applied Biosystems ® ). The qPCR cycling program was: Initial denaturation: 95°C, 5 min 35 cycles of: o Denaturation: 95°C, 1 min o Annealing / Extension / Data acquisition: 60°C, 45 sec

Figure 14 :

 14 Figure 14: Migration profile of the DNA ladder employed during electrophoresis This repartition of fragment s size of the BenchTop kb DNA ladder loaded within a 0.7% agarose electrophoresis gel.

  which is specific to one sample. During a single run, the Illumina MiSeq v3 system can produce up to 15 Gbp in paired sequences of 2x300 bp. So for each genome, around 1 million of pairs is sequenced. The length of a Thermococcus genome is on average 2 Mbp. We hence targeted a theorical average coverage of about 300X per nucleotide position. a) Libraries preparation The preparation of libraries was performed following the manufacturer protocol. The kit used is TruSeq ® DNA PCR-Free Library Prep (Ref: 15036187, revision D, Illumina ® ), with large insert length, i.e. 550 bp. For each sample, 2 µg of DNA was required. The first step was to fragment this genomic DNA. The DNA shearing was done with a M220 Focused-ultrasonicator™ Covaris ® ) (Figure 16). The sample was loaded in microTUBE AFA Fiber Snap-Cap 6x16 mm (Ref: 520045, Covaris ® ). The lysis was performed with the following settings: duty factor 20%; Displayed power 50 W; Duration 55 sec; Temperature 20°C.

Figure 16 :

 16 Figure 16: Covaris ® and Bioanalyzer instruments On the left side, the Covaris ® M220 Focused-ultrasonicator™ used to shear DNA, and on the right, the Bioanalyzer 2100 (Agilent Technologies) used to assess quality of Illimuna ® genomic libraries.

Figure 17 :

 17 Figure 17: General principle of Illumina sequencing Adapted from https://bitesizebio.com/13546/sequencing-by-synthesis-explaining-theillumina-sequencing-technology/

Figure 18 :

 18 Figure 18: Example of an electropherogram From top to bottom: Beginning, middle and end of the electropherogram. The beginning is chaotic and stabilizes at position 20-30. Then peaks are clear. At the end, it is no longer possible to distinguish between peaks.

Figure 19 : 1 (

 191 Figure 19: Example of Illumina ® read quality This figure shows the average quality of each read1 from the genome of Thermococcus sp. AMTc19 after quality control. Obtained with FastQC v0.11.5 and default parameters (http://www.bioinformatics.babraham.ac.uk/projects/fastqc/)

  a) Set of genomes In this work, the dataset was composed by 114 Thermococcales genomes. Among them, 40 came from public databases, 46 were sequenced during this project. The laboratory MBGE (Pasteur Institute, Paris, France) sequenced 27 additional genomes. The last genome belongs to a new Thermococcus strain isolated in the laboratory, Thermococcus sp. MF15 (Le Guellec et al., In Prep).

Figure 20 :

 20 Figure 20: Phylogenetic tree based on 16S rRNA gene-ITS sequences of UBOCC isolates This phylogenetic tree built by bayesian inference shows a summary of relationships between Thermococcales isolates present in UBOCC and genomes of Thermococcales available in public databases (Bold leaves). Red and Blue leaves represent isolates chosen for genome sequencing. Bootstrap values greater than 50 are shown next to nodes. Bar: 1 substitution per 100 nucleotides.

Figure 21 :

 21 Figure 21: Geographic origins of isolates selected for whole genome sequencing Isolates of the group I come from the East Pacific Rise (EPR) 13°N, the Rainbow deepsea vent site and the Saint-Paul hot spring. Isolates of the group II come the EPR 9°N and the EPR 13°N (R Core Team, 2015; Wickham, 2009).

Figure 22 :

 22 Figure 22: Examples of normal vs. potential mobile genetic elements coveragesFor each line, the pink curve shows the genome coverage at a given position. The highest value is displayed on the left. For Thermococcus sp. EXT11c, the mean genome coverage is about 230X while there is a 13 kb region experiencing a 10-fold coverage increase, suggesting the presence of a mobile genetic element present in multiple copies within the cell and also inserted in the chromosome. Thermococcus sp. EXT08c contig 1: the mean genome coverage (about 148X); contigs 3 and 4: the coverage of two suspected mobile genetic elements, 1180X and 600X respectively.

Figure 23 :

 23 Figure 23: Pangenomics analysis of 114 Thermococcales genomes On this figure, genomes are displayed as circle layers: 14 Pyrococcus, 95 Thermococcus, and 2 Palaeococcus. Each leaf of the centered dendrogram represents a PC, organized by hierarchical clustering based on their presence/absence across genomes. When a PC is present within a genome, it results in the presence of a dark colored bar on the genome s layer. On the upper right, are displayed metadata: G+C content, length and the number of genes for each genome. The Completion and Redundancy are two metrics to assess the quality of the genome assembly. They are based on a dataset of 162 archaeal single-copy genes (Rinke et al., 2013). Redundancy reflects the multiple occurrence of

  ,D), 5 potentially new ones and 14 strains belonging to T. nautili species. These 6 species are highlighted by different branches colors on the phylogenetic tree (Figure 24B), and were named as follow (descending order in the tree, figure B Nautili-, Nautili-, Nautili-, Nautili-, Nautili-, and Nautili-. Four of them are only present within one hydrothermal site, while Nautili-and Nautili-are present over the two EPR °N and EPR 13°N hydrothermal sites. e) What are the consequences of the differentiations at the genomic level?

Figure 25 :

 25 Figure 25: Genomic similarity of isolates from groups I and II A,B: ANI 96% threshold. C,D: DDH 70% threshold. A,C: Group I. B,D: Group II. Each legend is displayed between heatmaps.

Figure 26 :

 26 Figure 26: Group I pan-genome overview Group I pan-genome comprised 3 948 PCs (49 945 genes). On this pan-genome, genomes (concentric circles) are grouped as species defined previously, and colored based on their geographic origin. They are organized based on the SCGs phylogeny. Bins, outermost layer, represent PCs specific to a geographical cluster and / or species.

Figure 27 :

 27 Figure 27: Group II pan-genome overview Group II pan-genome comprises 4255 PCs (74 782 genes). Here, genomes (concentric circles) are colored as separated species, and organized based on the SCGs phylogeny. Bins (outermost layer) represent PCs specific to a species.

  different places: 259 from Juan de Fuca (JdF) in North Pacific Ocean (AxialSeamount), 52 from the Cayman rise, 12 from Lau Basin in South Pacific Ocean, 3 from Menez Gwen at the Mid Atlantic Ridge MAR , from Lost City at the MAR, from Loki s castle in North Atlantic, 3 from the Guaymas Basin, for the deep-sea context. Two other metagenomes were obtained from the bay of Prony in New Caledonia, from shallow and low temperature hydrothermal vents. Then, the remaining metagenomes were sampled from hot springs: 11 metagenomes sampled in the Yellowstone National Park, 3 from Taïwan, 2 from South Africa, 1 from Malaysia and 1 from Oklahoma (USA) (Appendix 2). All these metagenomes were mapped onto 102 Thermococcales genomes distributed as follow: 1 Palaeococcus, 18 Pyrococcus and 83 Thermococcus. These 102 Thermococcales genomes corresponded to the 46 genomes sequenced during this project, the 26 unpublished genomes (7 Pyrococcus and 19 Thermococcus), and all 30 published genomes publicly available at the time of the study (1 Palaeococcus, 11 Pyrococcus and 18 Thermococcus).

Figure 28 :

 28 Figure 28: Mapping of metagenomes on Thermococcales genomes This figure shows the detection of 102 Thermococcales genomes in 354 metagenomes (hydrothermal vent and terrestrial hot spring), that is the proportion of a given genome that is covered at least 1X. The colored scale ranges from 0% (light grey), to 1% of detection (black). Each layer of the disk represents a genome; they are ordered based on their taxonomy: Red = Palaeococcus, Green = Pyrococcus, Blue = Thermococcus. Each radius represents a metagenome or metatranscriptome, and replicates are grouped at the same place on the figure. JdF: Juan de Fuca.

  . Thermococcus guaymasensis sp. nov. and Thermococcus aggregans sp. nov., two novel thermophilic archaea isolated from the Guaymas Basin hydrothermal vent site. Int. J.Syst. Bacteriol. 48, 1181-1185. (2002). Changes in archaeal, bacterial and eukaryal assemblages along a salinity gradient by comparison of genetic fingerprinting methods in a multipond solar saltern. Environ. Microbiol. 4, 338-348. Case, R.J., Boucher, Y., Dahllöf, I., Holmström, C., Doolittle, W.F., and Kjelleberg, S. (2007). Use of 16S rRNA and rpoB Genes as Molecular Markers for Microbial Ecology Studies. Appl. Environ. Microbiol. 73, 278-288. , L.M., et al. (2015). Genomic Expansion of Domain Archaea Highlights Roles for Organisms from New Phyla in Anaerobic Carbon Cycling. Current Biology 25, 690-701. Castelle, C.J., and Banfield, J.F. (2018). Major New Microbial Groups Expand Diversity and Alter our Understanding of the Tree of Life. Cell 172, 1181-1197.Chan, C.S., Chan, K.-G., Tay, Y.-L., Chua, Y.-H., and Goh, K.M. (2015). Diversity of thermophiles in a Malaysian hot spring determined using 16S rRNA and shotgun metagenome sequencing. Front. Microbiol. 6. Chien, A., Edgar, D.B., and Trela, J.M.

Figure 1 :

 1 Figure 1: Exemple de cheminée hydrothermale. Le fluide sortant d e ces édifices a une température d'environ 200 à 300 °C alors que l'eau d e mer est elle à 2 °C. Cette différence brutale de température entraine la précipitation des éléments minéraux présents dans le fluide.

Figure 3 :

 3 Figure 3: Lieux d'échantillonage des 23 souches apparentées à l'espèce Thermococcus nautili. Les isolats ont été récolté lors de 3 campagnes océanographiques, deux sur l'océan Pacifique et une sur l'océan Atlantique, totalisant 4 sites hydrothermaux.

Figure 2 :

 2 Figure 2: Photos d'un Thermococcus. A,B microscopie à transmission; C,D microscopie à balayage. Les Thermococcus sont des coques d'environ 1 µm de diamètre, ils ne supportent pas l'oxygène (anaérobie), et se nourrissent de sucres, protéines et lipides. Ils sont également capables de se déplacer grâce à leurs flagelles (A,B). (d'après[START_REF] Dalmasso | Thermococcus piezophilus sp. nov., a novel hyperthermophilic and piezophilic archaeon with a broad pressure range for growth, isolated from a deepest hydrothermal vent at the Mid-Cayman Rise[END_REF]

Figure 4 :

 4 Figure 4: Arbre phylogénétique de l'ordre des Thermococcales. Cet ordre comprend l es g enres Pyrococcus, Palaeococcus e t Thermococcus. La population de génomes utilisée dans l a présente étude est située dans l'encadré b leu. L'arbre phylogénétique a été construit e n utilisant les séquences du gène codant pour la petite sous-unité de l'ARN ribosomal (ARNr 16S) de chaque souche analysée ainsi que les souches référencées dans les bases de données.

Figure 5 :

 5 Figure 5: Comparaison des génomes réalisée avec Anvi'o[START_REF] Eren | Anvi'o: an advanced analysis and visualization platform for 'omics data[END_REF]. Chaque piste correspond à un isolat, et chaque trait correspond à un groupe de protéines. L'arbre au centre représente une hiérarchisation de ces groupes. Un groupe est composé de protéines similaires retrouvées dans un ou plusieurs génomes. En haut à droite sont présentées les différentes métadonnées des génomes et des isolats. 1) Génome-coeur ,c'est à dire l'ensemble des gènes partagés par tous les isolats étudiés. 2) Une partie des gènes accessoires présents uniquement au sein d'isolats du Pacifique. 3) Gènes spécifiques de l'isolat IRI06c, provenant de l'Atlantique.

  Tous les ADN ont été extraits au laboratoire. Une moitié des génomes a directement été envoyée au Marine Biological Laboratory (MBL) à Woods Hole, USA, pour séquençage. Concernant la seconde moitié des génomes, les banques Illumina ont été préparées au laboratoire, puis envoyées au MBL pour séquençage. Nous avons choisi un séquençage sur Illumina MiSeq en paired-end reads 2x300 pb. J ai ensuite assemblé les génomes à l aide de CLC Genomics Workbench, en utilisant différentes tailles de k-mer. Au total 46 génomes ont été assemblés avec succès, dont 19 avec un seul contig circulaire, 15 avec un contig non circularisé et 13 génomes demeuraient fragmentés (2 à 57 contigs). Le séquençage a échoué pour un génome du group I (MC5), et il semble que le génome de l isolat Thermococcus sp. E15P25 (groupe II) était contaminé, deux génomes semblant être présents, rendant sont utilisation impossible. Dans un second temps, nous avons construit un arbre phylogénomique afin de mettre tous ces génomes dans un contexte évolutif. Cet arbre avait un second objectif, vérifier que ces génomes s organisaient bien suivant les groupes définis avec les marqueurs ARNr 16S et ITS. Afin de construire une phylogénie solide, l ensemble des génomes de Thermococcales disponibles a été utilisé. La phylogénie réalisée était basée sur les gènes du core-génome présents en simple copie, car c est un jeu de donnée riche et défini sans a priori sur la fonction des gènes. Pour obtenir ce set de gènes, il a fallu réaliser une analyse de pangénomique, qui a permis de définir d une part, l ensemble des gènes partagés par tous les génomes étudiés (= core-génome , et d autre part l ensemble des autres gènes, soit le génome accessoire. L union de ces deux catégories a formé le pangénome. Ce dernier a été établi avec anvi o. Brièvement, anvi o détecte les séquences codantes (CDS) dans tous les génomes, puis compare toutes les séquences elles. Ce résultat était ensuite fourni à MCL, un algorithme qui regroupe les gènes via une géographique n expliquant pas leur organisation dans cet arbre. Le second paramètre qui a été étudié est la présence d espèce s microbienne, via les deux métriques que sont l AN) (identité nucléotidique moyenne entre les génomes) et l hybridation ADN ADN (DDH) communément utilisées pour la délinéation des espèces. Le groupe I comptait 7 espèces selon ces deux métriques : une par origine géographique, sauf pour le site Rainbow, qui comptait 3 espèces sympatriques (Figure 25). Le groupe II était composé, quant à lui, de 6 espèces, toujours suivant l AN) et la DDH (Figure 25). La dernière étape de cette étude a consisté à identifier les gènes et les voies métaboliques spécifiques résultants des processus évolutifs de différentiation. Pour chaque groupe, un nouveau pangénome a été établi (Figures 26-27). À partir de là, l objectif a ensuite été d identifier les gènes spécifiques à chaque espèce et d identifier les fonctions uniquement retrouvées dans ces gènes. En résumé, il y avait un nombre très variable de gènes spécifiques, de 1 à 336 suivant les espèces. De façon remarqualble, la moitié n avait pas d annotation. Parmi les gènes restants, beaucoup de fonctions étaient redondantes entre les espèces. Néanmoins, des fonctions uniques ont été identifiées : elles étaient majoritairement associées au métabolisme des acidesaminés, au métabolisme énergétique, au métabolisme des sucres ou encore au transport d ions inorganiques. Ces résultats ont apportés des éléments d information sur les pressions de sélections qui peuvent s appliquer sur ces micro-organismes dans les environnements profonds. Ceci nous a également renseigné sur les métabolismes acquis ou perdus qui entrainent la formation de nouvelles espèces microbiennes dans l environnement hydrothermal marin profond. La dernière partie de cette thèse portait sur la dissémination des Thermococcales dans l environnement. Pour ce faire, des métagénomes et métatranscriptomes provenant d environnements hydrothermaux profonds et de sources chaudes terrestres ont été alignés sur des génomes de Thermococcales Figure . Dans l ensemble, les génomes ont été retrouvés dans les métagénomes des fonds marins mais pas dans ceux des sources chaudes terrestres, la barrière entre ces deux environnements étant sans doute trop complexe à franchir par le simple fait de la dispersion aléatoire. Contrairement aux Thermococcus, les genres Pyrococcus et Palaeococcus ont été beaucoup moins détectés dans les métagénomes. Ceci laisse présager de niches écologiques plus restreintes et d une faible abondance de ces Archées dans l environnement. Enfin, certaines souches de Thermococcus, telles que T. cleftensis, semblaient quant à elles présenter une distribution plus comsmopolite (Pacifique Nord-Est et fosse des Caïmans en Atlantique), ce qui suggère qu elles seraient capables de migrer sur de longues distances, alors que d autres souches semblent ne rester qu au niveau d un seul site, ou qu elle colonisent des niches au spectre écologique plus répandus. Le caractère novateur de cette dernière étude en outre était de donner des pistes de recherche afin d isoler de nouveaux taxons intéressants, comme des Palaeococcus, faiblement représentés par rapport à l immense majorité de Thermococcus isolés, caractérisés et séquencés.

Table 1 :

 1 List of all Thermococcales species characterized to date ............................................

Table 2 :

 2 Genomic characteristics of publicly available complete Thermococcales

  Members of Thermococcus are split into two groups: the main with a mean G+C value of 54% [51.1 -56.4], and the second group, composed of 6 genomes, has a mean GC% value of 42%

An additional set of 12 genomes is available in public databases, but they are assembled at scaffold or contig level. Thermococcales have a single chromosome, with a mean genome length around 2 000 000 base pairs (bp). The largest genome to date is Thermococcus barophilus CH5 (2.39 Mbp) and the smallest one is Thermococcus sp. P6

(1.52 Mbp)

. The percentage of G+C is on average 42% for Pyrococcus species, with the exception of Pyrococcus yayanosii (51.6 %). Concerning Palaeococcus, the 2 available genomes have different G+C content: 43% for P. pacificus and 54% for P. ferrophilus.

Table 1 : List of all Thermococcales species characterized to date

 1

	Reference	(Dirmeier et al., 1998)
	Species	acidaminovorans
	Genus	Thermococcus

According to: http://www.bacterio.net/ and NCBI Taxonomy, https://www.ncbi.nlm.nih.gov/taxonomy

Table 2 : Genomic characteristics of publicly available complete Thermococcales genomes

 2

	Species	Strain	Size (Mb)	GC (%) Plasmid Accession	Ref
	Palaeococcus pacificus	DY20341	1.86	43		CP006019	(Zeng et al., 2015)
	Pyrococcus abyssi	GE5	1.77	44.7	1	AL096836	(Cohen et al., 2003)
	Pyrococcus chitonophagus	GC74	1.96	44.9		CP015193	(Oger, 2018)
	Pyrococcus chitonophagus	GC74	1.97	44.9		LN999010 (Papadimitriou et al., 2016)
	Pyrococcus furiosus	DSM 3638	1.91	40.8		AE009950	(Maeder et al., 1999)
	Pyrococcus furiosus	COM1	1.91	40.8		CP003685	(Bridger et al., 2012)
	Pyrococcus horikoshii	OT3	1.74	41.9		BA000001 (Kawarabayasi et al., 1998)
	Pyrococcus kukulkanii	NCB100	1.98	44.6		CP010835	(Oger et al., 2017)
	Pyrococcus sp. NA2	NA2	1.86	42.7		CP002670	(Lee et al., 2011)
	Pyrococcus sp. ST04	ST04	1.74	42.3		CP003534	(Jung et al., 2012a)
	Pyrococcus yayanosii	CH1	1.72	51.6		CP002779	(Jun et al., 2011)
	Thermococcus barophilus	MP	2.06	41.7	1	CP002372	(Vannier et al., 2011)
	Thermococcus barophilus	CH5	2.39	41.8		CP013050	(Oger et al., 2016)
	Thermococcus barossii	SHCK-94	1.92	54.7		CP015101	(Oger, 2018)
	Thermococcus celer	Vu 13	1.87	56.4		CP014854	(Oger, 2018)
	Thermococcus cleftensis	CL1	1.95	55.8		CP003651	(Jung et al., 2012b)
	Thermococcus eurythermalis	A501	2.13	53.5	1	CP008887	(Zhao et al., 2015)
	Thermococcus gammatolerans	EJ3	2.05	53.6		CP001398	(Zivanovic et al., 2009)
	Thermococcus gorgonarius	W-12	1.67	51.7		CP014855	(Oger, 2018)
	Thermococcus guaymasensis	DSM 11113	1.92	52.9		CP007140	(Zhang X. et al., 2014)
	Thermococcus kodakaraensis	KOD1	2.09	52		AP006878	(Fukui et al., 2005)
	Thermococcus litoralis	DSM 5473	2.22	43.1		CP006670	(Gardner et al., 2012)
	Thermococcus nautili	30-1	1.98	54.8	3	CP007264	(Oberto et al., 2014)
	Thermococcus onnurineus	NA1	1.85	51.3		CP000855	(Lee et al., 2008)
	Thermococcus pacificus	P-4	1.79	54.2		CP015102	(Oger, 2018)
	Thermococcus paralvinellae	ES1	1.96	40.3		CP006965	Jung et al., 2013
	Thermococcus peptonophilus	OG-1	1.90	51.7	1	CP014750	(Oger, 2018)
	Thermococcus piezophilus	CDGS	1.93	51.1		CP015520	(Dalmasso et al., 2016b)
	Thermococcus profundus	DT 5432	2.04	53.1	1	CP014862	(Oger, 2018)
	Thermococcus radiotolerans	EJ2	1.87	55.6		CP015106	(Oger, 2018)
	Thermococcus sibiricus	MM 739	1.85	40.2		CP001463	(Mardanov et al., 2009)
	Thermococcus siculi	RG-20	2.03	55		CP015103	(Oger, 2018)
	Thermococcus sp. 2319x1	2319x1	1.96	44.6		CP012200	(Gavrilov et al., 2016)
	Thermococcus sp. 4557	4557	2.01	56.1		CP002920	(Wang et al., 2011)
	Thermococcus sp. 5-4	5-4	1.85	55.7		CP021848	(Cossu et al., 2017)
	Thermococcus sp. AM4	AM4	2.09	54.8		CP002952	(Oger et al., 2011)
	Thermococcus sp. P6	P6	1.52	54.9		CP015104	(Oger, 2018)
	Thermococcus thioreducens	OGL-20P	2.07	53.5		CP015105	(Oger, 2018)

  Table 3 reports examples of phenotypes, determined by cultivating the isolate on lab bench, used to differentiate a new species of the genera Thermococcus.

Table 3 : Comparative table of phenotypic and genotypic differential characteristics

 3

	techniques are based on patterns of DNA on electrophoresis gels, like amplified
	fragment length polymorphism (known as AFLP) or Restriction Fragment Length
	Polymorphism (RFLP). In the latter technique, DNA samples are cleaved into smaller
	fragments by template-specific restriction enzymes. It is a kind of enzyme that cut DNA
	based on a specific template. The frequency of cuts depends on the length of this
	template. Then, for a sample, restrictions fragments are separated by length on

. Here, T. piezophilus was compared to 4 closed species of Thermococcus. ND: Not Determined. Adapted from

Dalmasso et al., 2016a

iii) Additional methods In 2002, the international committee on systematics of prokaryotes proposed new methods to strengthen the integrity of a microbial species. For instance, to sequence a minimum of 5 protein-encoding genes present in the majority of microorganisms (housekeeping genes). The G+C content of DNA can also be taken into account. Other

Table 4 : Speciation stages under different conditions of selections and homologous recombination From Shapiro and Polz, 2014

 4

  DNA Polymerase (Ref: M7845, Promega): 0.015 U.µL -1 Forward and Reverse primer: 0.2 µM 5X Green GoTaq ® Reaction Buffer (Ref: M791A, Promega): 1X Deoxynucleotides triphosphate (dNTP): 0.8 mM 1 µL of: DNA sample or negative control or positive control Sterile MiliQ ® water q.s.p 30 µL PCR products migrated on a 0.8% (w/v) agarose gel, at 100 V during 45 min. This gel was made with a Tris-Acatate-EDTA (TAE) buffer at concentration 1X. TAE and agarose

Table 6 : Summary of other genomes used in pangenomics study Strain Genome length (in bp) Genome G+C content (in %) Number of genes Group Accession Reference

 6

	Hong et al., 2015	Oberto J, Da Cunha V. and Forterre P	Oberto J, Da Cunha V. and Forterre P	Oberto J, Da Cunha V. and Forterre P	Oberto J, Da Cunha V. and Forterre P	Oberto J, Da Cunha V. and Forterre P	Oberto J, Da Cunha V. and Forterre P	Oberto J, Da Cunha V. and Forterre P	Oberto J, Da Cunha V. and Forterre P	Oberto J, Da Cunha V. and Forterre P
	NZ_LLYW00000000	-	-	-	-	-	-	-	-	-
	I	II	II	II	II	II	II	II	II	-
	2 626	2 169	2 145	2 164	2 188	2 238	2 253	2 247	2 279	1 874
	54.29	54.82	54.73	54.80	54.84	54.60	54.85	55.89	54.77	44.72
	2 337 139	1 922 260	1 924 085	1 969 639	1 976 351	2 013 327	2 021 135	2 030 483	2 048 119	1 720 484
	Thermococcus celericrescens	BPK M Thermococcus EXT09c	BPK P Thermococcus sp	BPK E Thermococcus 29 3	BKX A Thermococcus nautili	BPK A Thermococcus 33 3	BPK S Thermococcus 9 3	BPK B Thermococcus 26 2	BPK I Thermococcus E15p33	BPI D Pyrococcus GE 23

Figure 24: Phylogenomic tree of Thermococcales genomes

  A, Global Thermococcales phylogeny built by maximum likelihood under LG model. Green leaves represent genomes from public databases and black leaves those not published. Leaves highlighted in blue indicate group I and group II genomes and are highlighted in red. The dots on branches represent bootstrap values > 50, scale is 1 substitution per 1000 sites. B, left side: group II genomes sub-tree; right side: group I genomes sub-tree. Isolates geographic origins are displayed as colored bars adjacent to trees.

d) Do groups represent species or subspecies ?

  33 complete or near complete genomes, and 12 are fragmented in 2 two 57 contigs. The strains s genome size is around Mbp and they average 2100 genes. These values are in agreement with the other Thermococcales genomes. The Thermococcus genus is known to host a wide diversity of mobile genetic elements (for example (Gorlas

et al., 2013a; Kuprovic et al., 2013)

). In genome sequenced for this study, we found 19 potential mobile genetic elements. Interestingly, they are only present in genomes from the group II, which are close to T. nautili. In a 2004 survey where authors investigated the Thermococcales molecular diversity in EPR 13°N, they detected extracellular elements in 36 strains among 70 new isolates

Anantharaman, K., Breier, J.A., and

	reported as Pyrococcus sp. KOD1.	Anderson, R.E., Kouris, A., Seward,
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	Auch, A.F., Jan, M. von, Klenk, H.-P., and Göker, M. (2010a). Digital DNA-DNA hybridization for microbial species delineation by means of genome-to-genome sequence comparison. Stand.	R.J. (2017a). Structured Populations of Sulfolobus acidocaldarius with Susceptibility to Mobile Genetic Elements. Genome Biol. Evol. 9, 1699-1710.
	Genomic Sci. 2, 117.			Anderson,	R.E.,	Reveillaud,	J.,
	Amend, J.P., Meyer-Dombard, D.R., Sheth, S.N., Zolotova, N., and Amend, A.C. (2003). Palaeococcus helgesonii sp. nov., a facultatively anaerobic, Auch, A.F., Klenk, H.-P., and Göker, M. (2010b). Standard operating procedure for calculating genome-to-genome distances based on high-scoring segment pairs. Stand. Genomic Sci. 2, 142.	Reddington, E., Delmont, T.O., Eren, A.M., McDermott, J.M., Seewald, J.S., and Huber, J.A. (2017b). Genomic variation in microbial populations inhabiting the marine subseafloor at deep-sea hydrothermal vents. Nat. Commun. 8, 1114.
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List of all metagenomes mapped on Thermococcales genomes

	. polymerase thermophile Thermus aquaticus. J. Deoxyribonucleic acid from the extreme Bacteriol. 127, 1550-1557. Choi, D.H., Kwon, Y.M., Chiura, H.X., Yang, E.C., Bae, S.S., Kang, S.G., Lee, J.-H., Yoon, H.S., and Kim, S.-J. (2015). Extracellular Vesicles of the Hyperthermophilic Archaeon Thermococcus onnurineus NA T. Appl. Environ. Microbiol. 81, 4591-4599. Cohan, F.M. (2002). What are Bacterial Species? Annu. Rev. Microbiol. 56, 457--------EPR 13°N 13N Grandbonum PP-52 -EPR 13°N -EPR 13°N 13N Grandbonum PP-52 yes EPR 13°N 13N yes EPR 13°N 13N -EPR 13°N 13N -EPR 13°N 13N -EPR 13°N 13N -EPR 13°N 13N Totem -EPR 13°N 13N Totem -EPR 13°N 13N ---yes EPR 13°N 13N -EPR 13°N 13N yes EPR 13°N 13N Genesis PP-12 yes EPR 13°N 13N Genesis PP-12 -EPR 9°N -yes EPR 9°N -yes EPR 9°N -yes EPR 9°N -yes EPR 9°N --EPR 9°N --EPR 9°N ------------------cruise Starmer; site White lady -Mid Atlantic Ridge Menez Gwen -Mid Atlantic Ridge Menez Gwen -Mid Atlantic Ridge Menez Gwen ----Mid Atlantic Ridge Rainbow -Mid Atlantic Ridge Rainbow (IRIS 07) -Mid Atlantic Ridge Depth SRA ID Library type Reference 1500m SRR1688294 Metatranscriptomic -4940m ERR868108 Metagenomic Reveillaud et al., NA ERR420352 Metatranscriptomic -1522m ERR694384 Metatranscriptomic Fortunato and Huber, 1507m ERR694146 Metagenomic -1530m ERR694368 Metatranscriptomic -1521m ERR1163095 Metatranscriptomic -1514m ERR1163141 Metatranscriptomic -4940m ERR868109 Metagenomic NA ERR420353 Metagenomic -1522m ERR694390 Metatranscriptomic Fortunato and Huber, 1507m ERR694150 Metagenomic -1530m ERR694369 Metatranscriptomic -1521m ERR1163096 Metatranscriptomic -1514m ERR1163142 Metatranscriptomic -Reveillaud et al., NA ERR420354 Metagenomic -1543m ERR694126 Metagenomic -1507m ERR694127 Metagenomic -1530m ERR694370 Metatranscriptomic -1521m ERR1163097 Metatranscriptomic -1514m ERR1163143 Metatranscriptomic -4940m ERR868110 Metagenomic Reveillaud et al., NA ERR420355 Metatranscriptomic -1522m ERR694207 Metagenomic Fortunato and Huber, 1507m ERR694128 Metagenomic -1917m ERR694184 Metagenomic -1521m ERR1163098 Metatranscriptomic -2605m SRR1217367 Metagenomic Anantharaman et al., 4940m ERR868111 Metagenomic Reveillaud et al., NA ERR420356 Metatranscriptomic -1522m ERR694208 Metagenomic Fortunato and Huber, 1507m ERR694130 Metagenomic -1917m ERR694185 Metagenomic -1521m ERR1163099 Metatranscriptomic -1890m SRR1217452 Metagenomic Anantharaman et al., Rainbow (IRIS 07) -Mid Atlantic Ridge Rainbow (IRIS 07) -Mid Atlantic Ridge Rainbow (IRIS 07) -Mid Atlantic Ridge Rainbow (IRIS 07) -Mid Atlantic Ridge Rainbow (IRIS 07) -Mid Atlantic Ridge Rainbow (IRIS 07) --1500m SRR1688295 Metatranscriptomic -1500m SRR1688296 Metatranscriptomic -1500m SRR1688298 Metatranscriptomic -1500m SRR1688300 Metatranscriptomic -1500m SRR1688303 Metatranscriptomic -4940m ERR868112 Metagenomic Reveillaud et al., NA ERR420357 Metagenomic -1522m ERR694209 Metagenomic Fortunato and Huber, 1507m ERR694131 Metagenomic -1917m ERR694191 Metagenomic -1521m ERR1163100 Metatranscriptomic -2440m SRR1217459 Metagenomic Anantharaman et al., 4940m ERR868113 Metagenomic NA ERR420362 Metatranscriptomic -1522m ERR694210 Metagenomic Fortunato and Huber, 1507m ERR694138 Metagenomic -1917m ERR694196 Metagenomic -1521m ERR1163101 Metatranscriptomic -1960m SRR1217460 Metagenomic Anantharaman et al., Reveillaud et al., NA ERR420363 Metagenomic -1522m ERR694211 Metagenomic Fortunato and Huber, 1507m ERR694139 Metagenomic -1917m ERR694197 Metagenomic -1521m ERR1163102 Metatranscriptomic -1919m SRR1217462 Metagenomic Anantharaman et al., 4940m ERR868114 Metagenomic Reveillaud et al., NA ERR420365 Metagenomic -1522m ERR694212 Metagenomic Fortunato and Huber, 1507m ERR694141 Metagenomic -1917m ERR694186 Metagenomic -1521m ERR1163103 Metatranscriptomic -2155m SRR1217463 Metagenomic Anantharaman et al., 4940m ERR868115 Metagenomic Reveillaud et al., NA ERR420368 Metagenomic -1522m ERR694213 Metagenomic Fortunato and Huber, 1507m ERR694143 Metagenomic -1917m ERR694178 Metagenomic -1521m ERR1163104 Metatranscriptomic -2229m SRR1217465 Metagenomic Anantharaman et al., --Mid Atlantic Ridge 1500m SRR1688306 Metatranscriptomic -Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868031 Pyrococcus 100% Pyrococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% --Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Thermococcus 100% Pyrococcus 100% Pyrococcus 100% Pyrococcus 100% --------Thermococcus 100% Pyrococcus 100% Pyrococcus 100% Pyrococcus 100% --Pyrococcus 100% Thermococcus 100% Thermococcus 100% Appendix 2: Sample type yes 549 yes AMTc 01 yes AMTc 02 yes AMTc yes AMTc yes AMTc yes AMTc yes AMTc yes AMTc yes AMTc yes AMTc yes AMTc yes AMTc no AMTc yes AMTc yes AMTc yes AMTc yes EXT 09c yes EXT 10c yes EXT 11c yes EXT 12c yes EXT 13c yes EXT 15c yes EXT 16c yes GE 01 yes GE 02 no GE 03 no GE 05 no GE 05a no GE 06 yes IRI 37c yes IRI 38c yes IRI 39b yes IRI 40b no IRI 42c yes IRI 43a yes IRI 44a yes Location deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca rise deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca rise deep_sea_hydrothermal_vent deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca Shrimp Gulley #2, Piccard, Mid Cayman rise deep_sea_hydrothermal_vent deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Kilo Moana, Lau Bassin Shrimp Gulley #2, Piccard, Mid Cayman deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Mariner, Lau Bassin rise IRI 45a yes Thermococcus 100% IRI 47a yes Thermococcus 100% IRI 48a yes Thermococcus 100% IRI 49a yes Thermococcus 100% IRI 50a yes Thermococcus 100% IRI 51a no --deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Kilo Moana, Lau Bassin rise deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Abe, Lau Bassin rise deep_sea_hydrothermal_vent deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Tui Malila, Lau Bassin Shrimp Gulley #2, Piccard, Mid Cayman rise deep_sea_hydrothermal_vent deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Abe, Lau Bassin Shrimp Gulley #2, Piccard, Mid Cayman rise deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Tahi Moana, Lau Bassin IRI 52a yes Thermococcus 100% deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca deep_sea_hydrothermal_vent Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420366 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694200 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694147 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694176 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163105 Metagenomic -deep_sea_hydrothermal_vent Kilo Moana, Lau Bassin 2639m SRR1217564 Metagenomic Anantharaman et al., Rainbow (IRIS 07) 13N Grandbonum PP-52 AMTc 03 yes Thermococcus 100% -EPR 13°N AMTc yes Thermococcus 100% yes EPR 13°N 13N Genesis PP-12 GE 07 yes Pyrococcus 100% ---IRI 53a yes Thermococcus 100% -Mid Atlantic Ridge Rainbow (IRIS 07) deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688313 Metatranscriptomic deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868032 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420358 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694199 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694148 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694180 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163106 Metagenomic -deep_sea_hydrothermal_vent Abe, Lau Bassin 2159m SRR1217565 Metagenomic Anantharaman et al., -13N Grandbonum PP-52 AMTc 04 yes Thermococcus 100% -EPR 13°N 13N Genesis PP-12 AMTc 05 yes Thermococcus 100% -EPR 13°N 13N Genesis PP-12 AMTc 07 yes Thermococcus 100% -EPR 13°N 13N Genesis PP-12 AMTc 09 yes Thermococcus 100% yes EPR 13°N AMTc yes Thermococcus 100% yes EPR 13°N 13N Genesis PP-12 AMTc yes Thermococcus 100% -EPR 13°N 13N Genesis PP-12 AMTc yes Thermococcus 100% -EPR 13°N 13N Genesis PP-12 AMTc yes Thermococcus 100% -EPR 13°N 13N Pulsar PP-55 GE 08 yes Thermococcus 100% --cruise Starmer; site White IRI 54a yes Thermococcus 100% -Mid Atlantic Ridge Rainbow (IRIS 07) deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688314 Metatranscriptomic -deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868033 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420359 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694203 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694149 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694181 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163107 Metagenomic -deep_sea_hydrothermal_vent Mariner, Lau Bassin 1785m SRR1217567 Metagenomic Anantharaman et al., lady GE 18 no -----GE 19 yes Thermococcus 100% ---IRI 55a yes Thermococcus 100% -Mid Atlantic Ridge Rainbow (IRIS 07) IRI 56a yes Thermococcus 100% -Mid Atlantic Ridge deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688315 Metatranscriptomic -deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868034 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420360 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694111 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694360 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694182 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163108 Metagenomic -deep_sea_hydrothermal_vent Kilo Moana, Lau Bassin 2315m SRR1217566 Metagenomic Anantharaman et al., Rainbow (IRIS 07) IRI 57a yes Pyrococcus 100% -Mid Atlantic Ridge deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688316 Metatranscriptomic -deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868035 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420361 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694201 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694363 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694183 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163109 Metagenomic -deep_sea_hydrothermal_vent Tu'i Malila vent field, Lau bassin 1876m SRR4453772 Metagenomic Skennerton et al., 2015 Rainbow (IRIS 07) 13N Grandbonum PP-52 AMTc 10 yes Thermococcus 100% -EPR 13°N AMTc yes Thermococcus 100% yes EPR 13°N 13N Pulsar PP-55 GE 20 no -----IRI 58a yes Thermococcus 100% -Mid Atlantic Ridge Rainbow (IRIS 07) deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688317 Metatranscriptomic deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868036 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420364 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694202 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694365 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694187 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163110 Metagenomic -deep_sea_marine_sediment Loki's castle, GC14, Norwegian Sea 3283m SRR1555744 Metagenomic Spang et al., 2015 -13N Pulsar PP-55 AMTc 101 yes Thermococcus 100% -EPR 13°N 13N AMTc 102 yes Thermococcus 100% yes EPR 13°N 13N AMTc 11 yes Thermococcus 100% -EPR 13°N 13N Pulsar PP-55 AMTc 12 yes Thermococcus 100% -EPR 13°N AMTc yes Thermococcus 100% -EPR 13°N 13N La chainette PP-57 AMTc yes Thermococcus 100% -EPR 13°N 13N La chainette PP-57 AMTc yes Thermococcus 100% yes EPR 13°N 13N La chainette PP-57 AMTc yes Thermococcus 100% -EPR 13°N 13N Pulsar PP-55 GE 21 no -----GE 22 no ----IRI 59a yes Thermococcus 100% -Mid Atlantic Ridge Rainbow (IRIS 07) deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688318 Metatranscriptomic -deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868037 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420367 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694204 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694366 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694188 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163111 Metagenomic -deep_sea_marine_sediment Loki's castle, GC14, Norwegian Sea 3283m SRR1555743 Metagenomic Spang et al., 2015 -GE 23 yes Pyrococcus 100% ---GE 25 no -----IRI 60a yes Thermococcus 100% -Mid Atlantic Ridge Rainbow (IRIS 07) IRI 61a yes Thermococcus 100% -Mid Atlantic Ridge deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688319 Metatranscriptomic -deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868038 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694114 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694205 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694362 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694194 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163112 Metagenomic -deep_sea_marine_sediment Loki's castle, GC14, Norwegian Sea 3283m SRR1555748 Metagenomic Spang et al., 2015 Rainbow (IRIS 07) KAZA yes Thermococcus 100% -Mid Atlantic Ridge deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688320 Metatranscriptomic -deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868039 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694115 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694206 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694361 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694195 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163113 Metagenomic -deep_sea_hydrothermal_vent Lost city, Mid Atlantic Ridge 733m SRR1636508 Metagenomic -Rainbow 13N Pulsar PP-55 AMTc 13 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 14 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 15 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 16 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 17 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 18 yes Thermococcus 100% -EPR 13°N 13N La chainette PP-57 AMTc 19 yes Thermococcus 100% yes EPR 13°N 13N La chainette PP-57 AMTc 20 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 21 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 22 yes Thermococcus 100% -EPR 13°N 13N Elsa AMTc 23 yes Thermococcus 100% -EPR 13°N 13N Elsa AMTc 24 yes Thermococcus 100% -EPR 13°N 13N Elsa AMTc 26 yes Thermococcus 100% -EPR 13°N 13N Elsa AMTc 27 yes Thermococcus 100% -EPR 13°N 13N Elsa AMTc 29 yes Thermococcus 100% yes EPR 13°N 13N Elsa AMTc 30 yes Thermococcus 100% yes EPR 13°N 13N Genesis PP-12 AMTc 31 yes Thermococcus 100% -EPR 13°N 13N Genesis PP-12 AMTc 32 yes Thermococcus 100% -EPR 13°N 13N Genesis PP-12 AMTc 33 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 34 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 35 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 36 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 38 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 40 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 41 yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc 42 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 43 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 44 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 45 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 46 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 47 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 48 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc 49 yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc yes Thermococcus 100% -EPR 13°N 13N Pulsar PP-55 AMTc yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc yes Thermococcus 100% -EPR 13°N 13N Grandbonum PP-52 AMTc yes Thermococcus 100% yes EPR 13°N 13N La chainette PP-57 AMTc yes Thermococcus 100% yes EPR 13°N 13N La chainette PP-57 AMTc yes Thermococcus 100% -EPR 13°N 13N Elsa AMTc yes Thermococcus 100% -EPR 13°N 13N PP-Hot14 AMTc yes Thermococcus 100% -EPR 13°N GE 26 yes Pyrococcus 100% --cruise Starmer; site White m 13 no -----deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1500m SRR1688321 Metatranscriptomic -deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868040 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694116 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694377 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694364 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163068 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163114 Metagenomic -deep_sea_hydrothermal_vent Lost city, Mid Atlantic Ridge 766m SRR1636509 Metagenomic -lady GE 27 yes Pyrococcus 100% --cruise Starmer; site White lady GE 30 no -----GE 31 yes Thermococcus 100% ---GE 32 no -----IRI 01c yes Thermococcus 100% -Mid Atlantic Ridge Rainbow m 2 no -----m 20 no -----MC4 yes Thermococcus 100% yes South Indian Ocean Saint-Paul MC5 yes Thermococcus 100% yes South Indian Ocean Saint-Paul MC8 yes Thermococcus 100% yes South Indian Ocean deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman 4940m ERR868087 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868041 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694123 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694378 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694170 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163069 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163115 Metagenomic -terrestrial_hot_spring Sungai Klah, Malaysia 0m ERR372908 Metagenomic Chan et al., rise deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868088 Metagenomic deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868042 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694110 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694379 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694157 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163070 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163116 Metagenomic -deep_sea_hydrothermal_vent Menez Gwen, Mid Atlantic Ridge 828m ERR1078300 Metagenomic Meier et al., 2016 Reveillaud et al., deep_sea_hydrothermal_vent deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868043 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694112 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694380 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694154 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163071 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163117 Metagenomic -deep_sea_hydrothermal_vent Menez Gwen, Mid Atlantic Ridge 828m ERR1078301 Metagenomic Meier et al., 2016 Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868089 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868044 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694113 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694381 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694156 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163072 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163118 Metatranscriptomic -deep_sea_hydrothermal_vent Menez Gwen, Mid Atlantic Ridge 828m ERR1078302 Metagenomic Meier et al., 2016 Saint-Paul MC9 yes Thermococcus 100% yes South Indian Ocean Saint-Paul deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman 4940m ERR868090 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868045 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694117 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694121 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694160 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163073 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163119 Metatranscriptomic -hydrothermal_spring Bay of Prony, ST09, New Caledonia 43m SRR1636517 Metagenomic Mei et al., 2016 rise 13N Grandbonum PP-52 AMTc yes Thermococcus 100% -EPR 13°N 13N CIR 02c yes Thermococcus 100% -Indian Ocean -25; 75 CIR 03a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 04a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 05a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 06a yes Thermococcus 100% -Indian Ocean IRI 02c yes Thermococcus 100% -Mid Atlantic Ridge Rainbow IRI 03c yes Thermococcus 100% -Mid Atlantic Ridge Rainbow IRI 05c yes Thermococcus 100% -Mid Atlantic Ridge Rainbow IRI 06c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 07c yes Thermococcus 100% yes Mid Atlantic Ridge deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman 4940m ERR868091 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868046 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694118 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1516m ERR694382 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694161 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163074 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163120 Metatranscriptomic -hydrothermal_spring Bay of Prony, ST09, New Caledonia 43m SRR1636516 Metagenomic Mei et al., 2016 rise deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868092 Metagenomic deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868047 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694119 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694122 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694162 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163075 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163121 Metatranscriptomic -terrestrial_hot_spring Zodletone Spring, Oklahoma, USA 0m SRR5214155 Metagenomic -Reveillaud et al., deep_sea_hydrothermal_vent deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868048 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694177 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694124 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694163 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163076 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163122 Metatranscriptomic -terrestrial_hot_spring Limpopo, South Africa 0m SRR5214705 Metagenomic -Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868093 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868049 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694179 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694125 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694164 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163077 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163123 Metatranscriptomic -terrestrial_hot_spring Tshipise, South Africa 0m SRR5214706 Metagenomic -Rainbow IRI 09c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868094 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868050 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694189 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694356 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694165 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163078 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1539m ERR1163124 Metatranscriptomic -terrestrial_hot_spring Shi-Huang-Ping, Taïwan 0m SRR1297185 Metagenomic --25; 75 CIR 07a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 08a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 09a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 10a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 12a no ----IRI 10c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 14c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 15c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 17c yes Thermococcus 100% -Mid Atlantic Ridge Rainbow IRI 19c yes Thermococcus 100% -Mid Atlantic Ridge Rainbow deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman 4940m ERR868095 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868051 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694190 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694357 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694166 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163079 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163125 Metagenomic -terrestrial_hot_spring Shi-Huang-Ping, Taïwan 0m SRR1297186 Metagenomic -rise deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868096 Metagenomic deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868052 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694192 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694358 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694153 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163080 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163126 Metagenomic -terrestrial_hot_spring Shi-Huang-Ping, Taïwan 0m SRR1297203 Metagenomic -Reveillaud et al., deep_sea_hydrothermal_vent deep_sea_hydrothermal_vent Ginger Castle, Von Damm, Mid Cayman rise 2308m ERR868053 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694193 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694359 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694155 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1200m ERR1163081 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163127 Metagenomic -terrestrial_hot_spring Octopus Spring, Yellowstone National Park 0m SRR4030098 Metagenomic -Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868097 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Guaymas Bassin 1600m SRR453184 Metatranscriptomic Baker et al., 2013 deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694198 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694129 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694158 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163082 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163128 Metagenomic -terrestrial_hot_spring Beowulf Spring, Yellowstone National Park 0m SRR4030100 Metagenomic --CIR 14a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 15a yes Thermococcus 100% -Indian Ocean -25; 75 CIR 16a yes Thermococcus 100% -Indian Ocean -25; 75 E10p10 no -----E10p11 yes Thermococcus 100% yes EPR 9°N -E10p12 yes Thermococcus 100% -EPR 9°N -E10p13 no -----E10p14 yes Thermococcus 100% -EPR 9°N -E10p15 yes Thermococcus 100% -EPR 9°N -E10p2 yes Thermococcus 100% -EPR 9°N -E10p3 yes Thermococcus 100% -EPR 9°N -E10p4 yes Thermococcus 100% -EPR 9°N -E10p5 yes Thermococcus 100% -EPR 9°N -E10p6 yes Thermococcus 100% -EPR 9°N E10p7 yes Thermococcus 100% yes EPR 9°N -IRI 36c yes Thermococcus 100% yes Mid Atlantic Ridge Menez Gwen deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868107 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420351 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1522m ERR694389 Metatranscriptomic Fortunato and Huber, deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694144 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694372 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163094 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163140 Metatranscriptomic --IRI 21c yes Thermococcus 100% -Mid Atlantic Ridge Rainbow IRI 23c no -----IRI 24c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 25c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 26c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 27 c2 yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 29c yes Thermococcus 100% yes Mid Atlantic Ridge Rainbow IRI 30c yes Thermococcus 100% -Mid Atlantic Ridge deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868098 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman 4940m ERR868099 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Guaymas Bassin 1950m SRR452448 Metatranscriptomic Baker et al., 2013 deep_sea_hydrothermal_sediment Guaymas Bassin NA SRR5214303 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694376 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694373 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694135 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694137 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694167 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694168 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163083 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163084 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163129 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163130 Metagenomic terrestrial_hot_spring Mammoth Spring, Yellowstone National 0m SRR4030101 Metagenomic -Park -terrestrial_hot_spring Conch Spring, Yellowstone National Park 0m SRR4030102 Metagenomic -rise deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868100 Metagenomic deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420342 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694374 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694142 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694169 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163085 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163131 Metagenomic -terrestrial_hot_spring Grendel Spring, Yellowstone National Park 0m SRR4030106 Metagenomic -Reveillaud et al., deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868101 Metagenomic deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420343 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1543m ERR694120 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694145 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694159 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163086 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163132 Metagenomic -terrestrial_hot_spring Yellowstone National Park 0m SRR5207630 Metatranscriptomic -Reveillaud et al., deep_sea_hydrothermal_vent deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420344 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1917m ERR694375 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694151 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694171 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163087 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163133 Metagenomic -terrestrial_hot_spring Yellowstone National Park 0m SRR5207631 Metatranscriptomic -Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868102 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420345 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1522m ERR694387 Metatranscriptomic Fortunato and Huber, deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694152 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694174 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163088 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163134 Metagenomic -terrestrial_hot_spring Yellowstone National Park 0m SRR5207688 Metatranscriptomic -Rainbow IRI 31b yes Thermococcus 100% -Mid Atlantic Ridge Rainbow (IRIS 07) IRI 32b yes Thermococcus 100% -Mid Atlantic Ridge Rainbow (IRIS 09) IRI 33c yes Thermococcus 100% -Mid Atlantic Ridge Menez Gwen IRI 34c yes Thermococcus 100% -Mid Atlantic Ridge Menez Gwen IRI 35c yes Thermococcus 100% yes Mid Atlantic Ridge IRI 35c2 yes Thermococcus 100% yes Mid Atlantic Ridge Menez Gwen deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868106 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420350 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1522m ERR694388 Metatranscriptomic Fortunato and Huber, deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694140 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694371 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163093 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163139 Metatranscriptomic -Menez Gwen deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman 4940m ERR868103 Metagenomic Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420346 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1522m ERR694383 Metatranscriptomic Fortunato and Huber, deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694132 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694172 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163089 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163135 Metagenomic -terrestrial_hot_spring Yellowstone National Park 0m SRR5207689 Metatranscriptomic -rise deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868104 Metagenomic deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420347 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1522m ERR694385 Metatranscriptomic Fortunato and Huber, deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694133 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694173 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163090 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163136 Metatranscriptomic -terrestrial_hot_spring Yellowstone National Park 0m SRR5208581 Metatranscriptomic -Reveillaud et al., deep_sea_hydrothermal_vent Shrimp Gulley #2, Piccard, Mid Cayman rise 4940m ERR868105 Metagenomic deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420349 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1522m ERR694391 Metatranscriptomic Fortunato and Huber, deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694136 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694367 Metatranscriptomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163092 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163138 Metatranscriptomic -Reveillaud et al., deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca NA ERR420348 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1522m ERR694386 Metatranscriptomic Fortunato and Huber, deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1507m ERR694134 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1530m ERR694175 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1521m ERR1163091 Metagenomic -deep_sea_hydrothermal_vent Axial Seamount, Juan de Fuca 1514m ERR1163137 Metatranscriptomic -terrestrial_hot_spring Yellowstone National Park 0m SRR5248167 Metagenomic -

Acknowledgements

This thesis work was carried out at the Laboratoire de Microbiologie des Environnements Extrêmes (LM2E) at the Institut Universitaire Européen de la Mer (IUEM). It was financed by the Région Bretagne (Brittany Region) and Labex MER. I thank Mohamed Jebbar, Anne Godfroy and Didier Flament for welcoming me in this laboratory.

barophilus and BPK L Thermococcus Cir10a, both with an average detection rate of 1.5%.

The genus Palaeococcus represented here by P. pacificus was only detected in samples from JdF, Dependable hydrothermal field (JdF_2013_Dependable). Here an average of 9.5% of the genome was detected, which was the highest detection value forall genomes. Genomes of Pyrococcus were not detected frequently. Two isolates were more detected than the others: Pyrococcus sp. ST04 at on average 5% and 3% in metagenomes from Anemone hydrothermal site in JdF (JdF_2013_Anemone, JdF_2014_Anemone). The second best detected Pyrococcus was BPI E Pyrococcus sp.

IRI42c from Menez Gwen (MenezGwennMAR). An average of 1.5% of the genome was detected.

AUTHOR'S PERSONAL COPY

General synthesis

Conclusion

platform for omics data. PeerJ 3, e1319.

Ewing, B., and Green, P. (1998) Felsenstein, J. (1981). Evolutionary trees from DNA sequences: A maximum likelihood approach. J. Mol. Evol. 17, 368-376. Fiala, G., and Stetter, K.O. (1986). Pyrococcus furiosus sp. nov. represents a novel genus of marine heterotrophic archaebacteria growing optimally at 100°C. Arch. Microbiol. 145,[56][57][58][59][60][61]. (1987). Pyrococcus woesei, sp. nov., an ultra-thermophilic marine archaebacterium, representing a novel order, Thermococcales. Syst. Appl. Microbiol. 9, 62-70. Zivanovic, Y., Armengaud, J., Lagorce, A., Leplat, C., Guérin, P., Dutertre, M., Anthouard, V., Forterre, P., Wincker, P., and Confalonieri, F. (2009). Genome analysis and genome-wide proteomics of Thermococcus gammatolerans, the most radioresistant organism known amongst the Archaea. Genome Biol. 10, R70.

Appendix

Genomic diversity of closely related Thermococcus populations in deep-sea hydrothermal vent context

La définition de l espèce microbienne admise repose sur le pourcentage de réassociation ADN-ADN entre souches. Une valeur supérieure à 70% détermine l appartenance à la même espèce. Or ces valeurs seuils ne rendent pas toujours compte de la diversité fonctionnelle des populations. L utilisation de séquençage massif permet désormais l étude de nombreux génomes en parallèle. Ce travail se focalise sur l étude des variations intra vs interspécifique au niveau génomique fonctionnel. Ceci dans l objectif d apporter de nouvelles pistes de réflexions sur une définition des espèces cohérente du point de vue écologique et taxonomique. Une étude de génomique comparative a été menée sur deux clades qui appartiennent à un genre Archéen facilement isolable, le genre Thermococcus. Il est principalement retrouvé au niveau des environnements hydrothermaux océaniques profonds. Ces deux clades, représentant des espèces différentes, ont été sélectionnés dans une collection de 250 isolats de Thermococcus non caractérisés. Ces clades ont été retenus suivant deux critères: au moins une vingtaine d isolats et différentes origines géographiques. Les premiers résultats indiquent que l isolement géographique des membres du premier clade est un facteur de spéciation et d acquisition de différentes capacités métaboliques. Le second clade, dont un des membres est Thermococcus nautili, quant à lui, ne semble pas s engager dans cette voie. )l apparaît plutôt un maintien de plusieurs phylotypes dans le même environnement, certainement par la colonisation de microniches spécifiques.

Genomic diversity of closely related Thermococcus populations in deep-sea hydrothermal vent context

Microbial species definition is based, among others, on the percentage of DNA-DNA relatedness between strains. A value greater than 70% determines the membership of the same species. These thresholds do not always reflect the functional diversity of populations. The use of next-generation sequencing now allows studying many genomes in parallel. This work focuses on the study of intra and interspecific variations at the functional genomic level. The aim is to provide new pieces of reflection on a coherent species definition from an ecological and taxonomic point of view. A comparative genomic study was conducted on two clades that belong to an easily isolable archaeal genus: Thermococcus. It is mainly found in deep oceanic hydrothermal environments. These two clades, representing different species, were selected from a collection of 250 uncharacterized Thermococcus isolates. These clades were selected according to two criteria: at least twenty isolates and different geographical origins. Within the first clade, 20 genomes from 9°N East Pacific Ridge (EPR), Rainbow in mid Atlantic ridge and Saint-Paul island (south Indian Ocean), that represent 5 species according to the actual microbial species definition. Here, the geographical isolation explains the genomic divergence, and thus speciation, across members of this clade. The second clade is composed of 27 genomes close to Thermococcus nautili. These 27 isolates come from two hydrothermal site along the EPR: 9°N EPR and 13°N EPR. They represent 6 species according to DNA-DNA relatedness. Based on the phylogeny of single-copy core genes, these species or population co-occurred in both hydrothermal sites, suggesting colonization of different ecological niches. From the genomic comparative study, it appears that the main difference rely on the presence/absence of amino-acid biosynthesis pathway and transporters across the 6 populations. For example, the complete pathway for tryptophan biosynthesis is only present in 1 population (composed of 2 genomes). This maintenance of several phylotypes in the same environment may translate a recent or ongoing speciation event.

Synthèse de mes travaux