Johann Leplat
email: johann.leplat@culture.gouv.fr

Alexandre François

Faisl Bousta

Parengyodontium album, a frequently reported fungal species in the cultural heritage environment

Keywords: Parengyodontium album, Cultural heritage, Halotolerant species, Mesophilic species, Enzymes producer, Entomogenous species

Fungi are one of the main agents responsible for the biodeterioration of cultural heritage through physical and chemical processes. The frequent isolation of certain fungal species from deteriorated materials indicates that these species appear to have a particular affinity for environmental conditions occurring in cultural heritage. It is important to identify the conditions that favour the development of such species in order to understand how to preserve monuments and collections. Among these fungal species, the involvement of Parengyodontium album (Limber) Tsang et al. seems to have been underestimated until now.

This species is abundant in many environments and its taxonomic position has changed quite frequently, which may have concealed the effect of this fungus on cultural heritage sites. This review seeks to compile the involvement of P. album in cultural heritage biodeterioration phenomena under all the names that it has been attributed in order to effectively determine its occurrence. This paper also aims to determine whether P. album is marginal or dominant when detected on materials. Finally, the conditions that favour the development of P. album on cultural heritage objects and sites are discussed.

Introduction

The risk encountered by cultural heritage when colonized by fungal strains is widely known and recognized. Fungi can cause serious damage not only to buildings but also to their contents in the case of museums or libraries, whatever the nature of the material considered [START_REF] Sterflinger | Fungi: Their role in deterioration of cultural heritage[END_REF][START_REF] Sterflinger | Microbial deterioration of cultural heritage and works of arttilting at windmills?[END_REF]. First, fungi can cause aesthetic damage through staining or pigment discoloration [START_REF] Ciferri | Microbial degradation of paintings[END_REF][START_REF] Krumbein | Patina and cultural heritage-a geomicrobiologist's perspective[END_REF], as observed when black fungi grow on historical stones [START_REF] Cappitelli | Bacterial and fungal deterioration of the Milan Cathedral marble treated with protective synthetic resins[END_REF][START_REF] Isola | Extremotolerant rock inhabiting black fungi from Italian monumental sites[END_REF], or in the phenomenon known as "foxing" that occurs on historical papers [START_REF] Sterflinger | Microbial deterioration of cultural heritage and works of arttilting at windmills?[END_REF]. This initial aesthetic damage can be followed by more serious damage to the support [START_REF] Ciferri | Microbial degradation of paintings[END_REF]. Indeed, fungal growth can also lead to physical and chemical damage [START_REF] Scheerer | Microbial deterioration of stone monuments-an updated overview[END_REF][START_REF] Warscheid | Biodeterioration of stone: a review[END_REF]. Physical damage can occur when fungal hyphae enter the support through stone pores or through decayed stone parts and then by tunnelling into otherwise intact mineral material [START_REF] Gadd | Geomycology: biogeochemical transformations of rocks, minerals, metals and radionuclides by fungi, bioweathering and bioremediation[END_REF]. In painted surfaces, the growth of fungi through cracks and its migration below the paint layer can cause detachments [START_REF] Sterflinger | Fungi: Their role in deterioration of cultural heritage[END_REF]. Finally, the secretion of organic acids by fungi lead to chemical damage to the support, meaning that fungi are able to solubilize minerals [START_REF] Burford | Fungal involvement in bioweathering and biotransformation of rocks and minerals[END_REF][START_REF] Gadd | Geomycology: biogeochemical transformations of rocks, minerals, metals and radionuclides by fungi, bioweathering and bioremediation[END_REF][START_REF] Warscheid | Biodeterioration of stone: a review[END_REF]. Among the fungi observed in cultural heritage, we were surprised and above all intrigued by the frequent observation of the fungal species Parengyodontium album (Limber) Tsang et al. in several published and unpublished studies [START_REF] Leplat | White fungal covering on the wall paintings of the Saint-Savin-sur-Gartempe Abbey church crypt: A case study[END_REF][START_REF] Leplat | Aerobiological behavior of Paleolithic decorated caves: a comparative study of five caves in the Gard department (France)[END_REF]. The articles cited in this introduction provide a wide review of fungal biodeterioration on monuments as well as in museums, yet only [START_REF] Gadd | Geomycology: biogeochemical transformations of rocks, minerals, metals and radionuclides by fungi, bioweathering and bioremediation[END_REF] mentions P. album as a fungus that is frequently observed on stone. This review therefore aims to determine the true occurrence of P. album in cultural heritage and identify the factors that lead to this occurrence in cultural sites.

Brief history of Parengyodontium album taxonomy

Like many other fungal species, Parengyondontium album has had several successive names and changed fungal genus several times before being referred to by its current name. This species was first described as Tritirachium album [START_REF] Limber | caves (Nerja-Pintada system, southern Spain)[END_REF]. The new genus Tritirachium was created to describe fungal species bearing verticillately branched conidiophores like Verticillium, but which differ insofar that they have a final zigzag conidiabearing portion (Fig. 1). The genus included three species including Tritirachium album, which had been separated from a colony of Penicillium found on a book in a marine biological laboratory and had been considered as a possible contaminant.

The species was then renamed Beauveria alba and moved into the already existing Beauveria genus, which is also characterized by zigzag conidia-bearing portions because of the denticulation of its rachis and the absence of pigment in aerial mycelium [START_REF] Saccas | Etude morphologique et biologique d'un nouveau champignon papyricole, le Beauveria heimii sp[END_REF] The study of this new genus also revealed that the species Parengyondontium album probably includes several subclades. This article will exclusively use the name Parengyodontium album to describe this fungus.

Occurrence of Parengyodontium album in cultural heritage

3.1 Parengyodontium album: a worldwide distributed species Whatever the name used to describe it, Parengyodontium album has frequently been reported in historical buildings, museums, libraries and touristic sites. Its detection around the world shows that it is a ubiquitous fungal species (Fig. 3). It has been found on a Chilean world heritage site in southern America [START_REF] Ortiz | Deterioration, decay and identification of fungi isolated from wooden structures at the Humberstone and Santa Laura saltpeter works: a world heritage site in Chile[END_REF], in a Cuban museum in central America [START_REF] Borrego | Fungal assessment on storerooms indoor environment in the National Museum of Fine Arts, Cuba[END_REF], and in a show cave in north America [START_REF] Vaughan | Fungal communities on speleothem surfaces in Kartchner Caverns, Arizona, USA[END_REF]. The fungus has also been isolated across Europe from Portugal to Russia, with observations of its presence in England, Spain, France, Germany, Italy and Poland [START_REF] Jeffries | Growth of Beauvaria alba on mural paintings in Canterbury Cathedral[END_REF]Liñán et al., 2018;[START_REF] Nugari | Biodeterioration of mural paintings in a rocky habitat: The Crypt of the Original Sin (Matera, Italy)[END_REF][START_REF] Pfendler | Comparison of biocides, allelopathic substances and UV-C as treatments for biofilm proliferation on heritage monuments[END_REF][START_REF] Piotrowska | Abiotic determinants of the historical buildings biodeterioration in the former Auschwitz II -Birkenau concentration and extermination camp[END_REF][START_REF] Ponizovskaya | Micromycetes as colonizers of mineral building materials in historic monuments and museums[END_REF][START_REF] Schabereiter-Gurtner | Analysis of fungal communities on historical church window glass by denaturing gradient gel electrophoresis and phylogenetic 18S rDNA sequence analysis[END_REF][START_REF] Trovão | Fungal diversity and distribution across distinct biodeterioration phenomena in limestone walls of the old cathedral of Coimbra[END_REF]. Finally, P. album has also been detected in Africa and in Asia, but not in a cultural heritage-related environment [START_REF] Jaouani | Diversity and enzymatic profiling of halotolerant micromycetes from Sebkha El Melah, a Saharan salt flat in southern Tunisia[END_REF][START_REF] Zhang | Diverse deep-sea fungi from the South China Sea and their antimicrobial activity[END_REF].

Parengyodontium album: a species which develops on a great diversity of cultural sites and materials

The most commonly reported occurrences of Parengyodontium album are in religious monuments such as churches, cathedrals or monasteries (Table 1). A number of different materials are affected by the presence of the fungus in these monuments. The first of these materials is wall paintings: the fungus has been isolated on wall paintings located in the "aerial parts" of the monuments [START_REF] Jeffries | Growth of Beauvaria alba on mural paintings in Canterbury Cathedral[END_REF][START_REF] Sáiz-Jiménez | Microorganisms and environmental pollution as deteriorating agents of the frescoes of the Monastery of "Santa María de la Rábida[END_REF][START_REF] Sampo | A study of the fungi occurring on 15th century frescoes in Florence, Italy[END_REF] and also in the underground parts of the monuments such as the crypts [START_REF] Gorbushina | Distribution of microorganisms on ancient wall paintings as related to associated faunal elements[END_REF][START_REF] Leplat | White fungal covering on the wall paintings of the Saint-Savin-sur-Gartempe Abbey church crypt: A case study[END_REF]Fig. 4). The stone structure of buildings is also affected, as shown by the isolation of the fungus from the bare stone inside [START_REF] Karpovich-Tate | Microbial communities on damaged frescoes and building materials in the cathedral of the nativity of the virgin in the Pafnutii-Borovskii monastery[END_REF][START_REF] Pfendler | Comparison of biocides, allelopathic substances and UV-C as treatments for biofilm proliferation on heritage monuments[END_REF][START_REF] Pinheiro | Limestone biodeterioration: A review on the Portuguese cultural heritage scenario[END_REF] and outside the monument [START_REF] Saiz-Jimenez | Deposition of airborne organic pollutants on historic buildings[END_REF][START_REF] Trovão | Fungal diversity and distribution across distinct biodeterioration phenomena in limestone walls of the old cathedral of Coimbra[END_REF]. Historical glasswork is also affected, as shown by the isolation of P. album from the windows of Stockkämpfen church [START_REF] Schabereiter-Gurtner | Analysis of fungal communities on historical church window glass by denaturing gradient gel electrophoresis and phylogenetic 18S rDNA sequence analysis[END_REF].

Caves are the second kind of cultural sites in which P. album have frequently been reported.

The term "cave" covers a wide variety of different geological cases that vary from large caves that are several hundred meters deep to small sites that are around ten-meters deep or even simple rock shelters. The caves in which P. album has been isolated represent different aspects of cultural interest, ranging from caves known for their Paleolithic ornamentation, such as Lascaux cave in France [START_REF] Bastian | The microbiology of Lascaux cave[END_REF] to more recent Byzantine-style ornamentation, such as the crypt of the Original Sin in Italy [START_REF] Nugari | Biodeterioration of mural paintings in a rocky habitat: The Crypt of the Original Sin (Matera, Italy)[END_REF] and show caves visited for their geological interest [START_REF] Vaughan | Fungal communities on speleothem surfaces in Kartchner Caverns, Arizona, USA[END_REF]. Like in religious monuments, P. album was isolated in caves from wall paintings [START_REF] Nugari | Biodeterioration of mural paintings in a rocky habitat: The Crypt of the Original Sin (Matera, Italy)[END_REF], or directly from the bare rock [START_REF] Bastian | The microbiology of Lascaux cave[END_REF][START_REF] Lepinay | Biofilm communities survey at the areas of salt crystallization on the walls of a decorated shelter listed at UNESCO World cultural Heritage[END_REF][START_REF] Mihajlovski | Characterization of the archaeal and fungal diversity associated with gypsum efflorescences on the walls of the decorated Sorcerer's prehistoric cave[END_REF][START_REF] Nováková | Microscopic fungi isolated from the Domica Cave system (Slovak Karst National Park, Slovakia). A review[END_REF][START_REF] Vaughan | Fungal communities on speleothem surfaces in Kartchner Caverns, Arizona, USA[END_REF]. The novel difference observed in comparison with religious sites is that P. album has been abundantly detected not only on surfaces but also in the atmosphere of the caves [START_REF] Leplat | Aerobiological behavior of Paleolithic decorated caves: a comparative study of five caves in the Gard department (France)[END_REF]Liñán et al., 2018;[START_REF] Marvanová | Microscopic fungi in the Zbrašov aragonite caves[END_REF][START_REF] Nováková | Microscopic fungi isolated from the Domica Cave system (Slovak Karst National Park, Slovakia). A review[END_REF]. Finally, P. album was reported on a historical wood staircase located in a mine that dates back to the bronze and iron age in Austria [START_REF] Piñar | Biodeterioration risk threatens the 3100 year old staircase of Hallstatt (Austria): Possible involvement of halophilic microorganisms[END_REF], an environment that is comparable to that of caves. After wall paintings, stone, and glasswork, wood is therefore another kind of support that can be colonized by P. album.

The third group of cultural sites in which the presence of P. album has been reported is composed of all types of sepulchral site, i.e. from hypogean tombs dating from Etruscan and Roman times [START_REF] Saarela | Heterotrophic microorganisms in air and biofilm samples from Roman catacombs, with special emphasis on actinobacteria and fungi[END_REF][START_REF] Sprocati | A microbiological survey of the Etruscan Mercareccia tomb (Italy): contribution of microorganisms to deterioration and restoration[END_REF] to the tombstones of an historical Jewish cemetery [START_REF] Krumbein | Biological aspects of deterioration and consolidation of selected tombstones on Jewish cemeteries, 8th International Congress on Deterioration and Conservation of Stone[END_REF]. In environmental terms, hypogean tombs are cut in the rock and are thus are similar to caves, while tombstones show similar features to the external face of religious monuments, both being made of stone that is typically exposed to an urban environment. The phenomenon observed in caves has also been reported in the Christian catacomb of St. Domitillus in Rome, where P. album isolated from the air as well as from the wall paintings on marble, limestone and plaster supports [START_REF] Saarela | Heterotrophic microorganisms in air and biofilm samples from Roman catacombs, with special emphasis on actinobacteria and fungi[END_REF].

More recent historical buildings erected during the 20 th century are also affected by the presence of the fungus, which has been found in the barracks of the Auschwitz-Birkenau camp in Poland and in buildings at the Humberstone and Santa Laura saltpeter works in Chile [START_REF] Koziróg | Colonising organisms as a biodegradation factor affecting historical wood materials at the former concentration camp of Auschwitz II -Birkenau[END_REF][START_REF] Ortiz | Deterioration, decay and identification of fungi isolated from wooden structures at the Humberstone and Santa Laura saltpeter works: a world heritage site in Chile[END_REF][START_REF] Piotrowska | Abiotic determinants of the historical buildings biodeterioration in the former Auschwitz II -Birkenau concentration and extermination camp[END_REF]. In Auschwitz, P. album was isolated from mineral components such as plaster and brick and also from wooden parts. Similarly, P. album was isolated from wood in a building at Santa Laura saltpeter works; this is surprising given the location of the buildings in the Atacama Desert, an extreme environment characterized by dry conditions.

Finally, museums and libraries are also affected by the presence of the fungus, as shown by the isolation of P. album inside several of these buildings [START_REF] Borrego | Fungal assessment on storerooms indoor environment in the National Museum of Fine Arts, Cuba[END_REF][START_REF] Micheluz | The effects of book disinfection to the airborne microbiological community in a library environment[END_REF][START_REF] Ponizovskaya | Micromycetes as colonizers of mineral building materials in historic monuments and museums[END_REF][START_REF] Principi | Molecular studies of microbial community structure on stained pages of Leonardo da Vinci's Atlantic Codex[END_REF][START_REF] Trovão | Can arthropods act as vectors of fungal dispersion in heritage collections? A case study on the archive of the University of Coimbra, Portugal[END_REF]. In some cases, the fungus has been detected on the internal stone or plaster walls of the museums [START_REF] Ponizovskaya | Micromycetes as colonizers of mineral building materials in historic monuments and museums[END_REF], while it has been detected directly on artworks in other cases [START_REF] Borrego | Fungal assessment on storerooms indoor environment in the National Museum of Fine Arts, Cuba[END_REF]. These include samples of remarkable artworks such as Leonardo da Vinci's Atlantic Codex [START_REF] Principi | Molecular studies of microbial community structure on stained pages of Leonardo da Vinci's Atlantic Codex[END_REF], indicating that P. album can also be detected on paper. The fungus was indirectly detected in the Archives of the University of Coimbra, where it was isolated from an Araneae during a survey about arthropod-disseminated fungi [START_REF] Trovão | Can arthropods act as vectors of fungal dispersion in heritage collections? A case study on the archive of the University of Coimbra, Portugal[END_REF], and was also detected in an airborne form in the Library of Humanities of the Ca' Foscari University of Venice [START_REF] Micheluz | The effects of book disinfection to the airborne microbiological community in a library environment[END_REF].

To resume, Parengyodontium album has been detected on a wide variety of cultural heritage supports ranging from wall paintings, stone, plaster and brick to glass, wood and paper, and is even observed in an airborne form.

Parengyodontium album: associated symptoms and relative abundance on cultural heritage

Parengyodontium album has been associated with several different symptoms of deterioration in cultural heritage, without necessarily being considered to play a determining role in their development. Amongst these symptoms, the presence of soluble salt efflorescence has been the most frequently cited in relation to the fungus [START_REF] Ponizovskaya | Micromycetes as colonizers of mineral building materials in historic monuments and museums[END_REF][START_REF] Trovão | Fungal diversity and distribution across distinct biodeterioration phenomena in limestone walls of the old cathedral of Coimbra[END_REF]. The most commonly observed is gypsum, which can occur alone or be associated with organic compounds. However, P. album has also been isolated from calcium salts of oxalate, carbonate and chloride [START_REF] Lepinay | Biofilm communities survey at the areas of salt crystallization on the walls of a decorated shelter listed at UNESCO World cultural Heritage[END_REF][START_REF] Mihajlovski | Characterization of the archaeal and fungal diversity associated with gypsum efflorescences on the walls of the decorated Sorcerer's prehistoric cave[END_REF][START_REF] Saiz-Jimenez | Deposition of airborne organic pollutants on historic buildings[END_REF][START_REF] Sáiz-Jiménez | Microorganisms and environmental pollution as deteriorating agents of the frescoes of the Monastery of "Santa María de la Rábida[END_REF]. The second kind of symptoms associated with P. album is discoloration and patina (modification of the support colour) of various colors, including pink patina [START_REF] Berner | A comparative study of the fungal flora present in medieval wall paintings in the chapel of the castle Herberstein and in the parish church of St Georgen in Styria, Austria[END_REF][START_REF] Nugari | Biodeterioration of mural paintings in a rocky habitat: The Crypt of the Original Sin (Matera, Italy)[END_REF], ochre discoloration [START_REF] Berner | A comparative study of the fungal flora present in medieval wall paintings in the chapel of the castle Herberstein and in the parish church of St Georgen in Styria, Austria[END_REF], dark stains or black spots [START_REF] Bastian | The impact of arthropods on fungal community structure in Lascaux Cave[END_REF][START_REF] Sáiz-Jiménez | Microorganisms and environmental pollution as deteriorating agents of the frescoes of the Monastery of "Santa María de la Rábida[END_REF] and green-black patina [START_REF] Principi | Molecular studies of microbial community structure on stained pages of Leonardo da Vinci's Atlantic Codex[END_REF][START_REF] Trovão | Fungal diversity and distribution across distinct biodeterioration phenomena in limestone walls of the old cathedral of Coimbra[END_REF]. The fungus has also been associated with white covering that is visibly of fungal origin [START_REF] Bastian | The impact of arthropods on fungal community structure in Lascaux Cave[END_REF][START_REF] Leplat | White fungal covering on the wall paintings of the Saint-Savin-sur-Gartempe Abbey church crypt: A case study[END_REF].

Finally, P. album has been isolated from powdered historical stones (Karpovich-Tate and Rebrikova, 1991).

The abundance of P. album when detected on cultural heritage varied as much as the symptoms encountered or the materials affected. In some cases, P. album was the most abundant species isolated from deterioration symptoms, while in other cases only traces of the fungus were detected. In other studies, P. album was detected at varying levels of abundance along with other species. For example, P. album has often been the most abundant detected species when salt efflorescence (a coating caused by the migration of soluble salt contained in a porous material to the surface) was present [START_REF] Ponizovskaya | Micromycetes as colonizers of mineral building materials in historic monuments and museums[END_REF][START_REF] Trovão | Fungal diversity and distribution across distinct biodeterioration phenomena in limestone walls of the old cathedral of Coimbra[END_REF], but in other cases this species was noted simply as a relatively abundant secondary species [START_REF] Lepinay | Biofilm communities survey at the areas of salt crystallization on the walls of a decorated shelter listed at UNESCO World cultural Heritage[END_REF][START_REF] Mihajlovski | Characterization of the archaeal and fungal diversity associated with gypsum efflorescences on the walls of the decorated Sorcerer's prehistoric cave[END_REF][START_REF] Sáiz-Jiménez | Microorganisms and environmental pollution as deteriorating agents of the frescoes of the Monastery of "Santa María de la Rábida[END_REF]. [START_REF] Nugari | Biodeterioration of mural paintings in a rocky habitat: The Crypt of the Original Sin (Matera, Italy)[END_REF] failed to isolate the fungus on culture medium during their study of the pink patina on the Crypt of the Original Sin and finally identified it through SEM, yet it was the most abundant fungal species isolated by [START_REF] Berner | A comparative study of the fungal flora present in medieval wall paintings in the chapel of the castle Herberstein and in the parish church of St Georgen in Styria, Austria[END_REF] from a pink patina sample of the chapel of Herberstein Castle. This result does not suffice to confirm a role of P. album in the development of the pink patina, as the fungus was also abundantly isolated from ochre discoloration in the same study. However, these elements can indicate that this environment is globally favourable to the growth of P. album. The fungus has been abundantly isolated from the air of monuments when it was tested, and this was especially true of hypogean environments: P. album was one of the most abundant airborne fungi isolated in Roman catacombs of St. Domitilla and in the Nerja cave (Liñán et al., 2018;[START_REF] Saarela | Heterotrophic microorganisms in air and biofilm samples from Roman catacombs, with special emphasis on actinobacteria and fungi[END_REF], while it was only a secondary species in an air sample taken from a library in Venice [START_REF] Micheluz | The effects of book disinfection to the airborne microbiological community in a library environment[END_REF].

Particularities of cultural heritage environments that favour the development of Parengyodontium album

The microbial colonization of cultural heritage depends on environmental factors such as water availability, pH, climatic exposure, nutrient sources and the capacity of microorganisms to withstand possible sources of stress such as desiccation or UV radiation [START_REF] Scheerer | Microbial deterioration of stone monuments-an updated overview[END_REF][START_REF] Warscheid | Biodeterioration of stone: a review[END_REF]. Parengyodontium album is a chemoorganotrophic organism, and its development is dependent on its capacity to obtain organic compounds from an environment which is sometimes poor in nutrients, such as stone [START_REF] Gadd | Geomycology: biogeochemical transformations of rocks, minerals, metals and radionuclides by fungi, bioweathering and bioremediation[END_REF][START_REF] Sterflinger | Fungi: Their role in deterioration of cultural heritage[END_REF]. The central necessity is therefore to identify the common factors in the identified cultural heritage sites that can lead to the development of P. album.

Parengyodontium album: a species adapted to salty, moist environments

One of the principle factors in the growth of P. album seems to be the presence of salts on the supports it colonizes. Although the preceding paragraph notes that the fungus has been abundantly isolated directly from salt efflorescences, salts were also often present but not necessarily visible in other sites where the fungus grew. For example, the phenomenon of pink patina on historical stones and wall painting has been well documented to date.

Parengyodontium album is not the main agent of these discolorations, which are often related to bacterial biofilms [START_REF] Piñar | La vie en rose': a review of rosy discoloration of subsurface monuments[END_REF]. Sites affected by pink patina all have problems of water infiltration and salt crystallization, two phenomena that often occur simultaneously.

Problems of moisture and of water infiltration have also been widely observed on the walls of monuments from which P. album has been isolated [START_REF] Berner | A comparative study of the fungal flora present in medieval wall paintings in the chapel of the castle Herberstein and in the parish church of St Georgen in Styria, Austria[END_REF][START_REF] Karpovich-Tate | Microbial communities on damaged frescoes and building materials in the cathedral of the nativity of the virgin in the Pafnutii-Borovskii monastery[END_REF][START_REF] Leplat | White fungal covering on the wall paintings of the Saint-Savin-sur-Gartempe Abbey church crypt: A case study[END_REF][START_REF] Pfendler | Comparison of biocides, allelopathic substances and UV-C as treatments for biofilm proliferation on heritage monuments[END_REF][START_REF] Simonovicova | Engyodontium album, a new species of microscopic fungi for Slovakia and its keratinolytic activity[END_REF].

Moreover, airborne P. album has been repeatedly reported in caves, an environment known for relative humidity values that can sometimes approach 100 % (Liñán et al., 2018;[START_REF] Nováková | Microscopic fungi isolated from the Domica Cave system (Slovak Karst National Park, Slovakia). A review[END_REF]. This affinity of P. album for humid, salty environments is not a surprise since the fungus has often been isolated from the marine environment, including marine sediments [START_REF] Chellappan | Production, purification and partial characterization of a novel protease from marine Engyodontium album BTMFS10 under solid state fermentation[END_REF][START_REF] Kirichuk | Fungal assemblages of submarine soils of the eastern Sakhalin shelf[END_REF][START_REF] Yao | Cytotoxic polyketides from the deep-sea-derived fungus Engyodontium album DFFSCS021[END_REF][START_REF] Zhang | Diverse deep-sea fungi from the South China Sea and their antimicrobial activity[END_REF], marine sponges [START_REF] Wu | Engyodontochones, antibiotic polyketides from the marine fungus Engyodontium album strain LF069[END_REF], or directly from sea water [START_REF] Pindi | Diversity of fungi at various depths of marine water[END_REF]. P. album is therefore regarded as a halotolerant fungus that can grow on synthetic media supplemented with NaCl 20 % [START_REF] Ali | Identification and phylogenetic analysis of halophilic fungus isolated from a man-made solar saltern in Thailand[END_REF][START_REF] Jaouani | Diversity and enzymatic profiling of halotolerant micromycetes from Sebkha El Melah, a Saharan salt flat in southern Tunisia[END_REF].

Parengyodontium album: a mesophilic species

Little data is available concerning the effect of temperature on the growth of Parengyodontium album. The fungus is generally considered mesophilic [START_REF] Airaudi | Fungal biodiversity in the air of Turin[END_REF][START_REF] Xia | Insights into the role of electrostatics in temperature adaptation: a comparative study of psychrophilic, mesophilic, and thermophilic subtilisin-like serine proteases[END_REF]. Although P. album is capable of surviving at sub-zero temperatures, as proved by multiple observations of this species in Arctic and Antarctic environments, it is unable to grow at 0 °C [START_REF] Bergero | Psychrooligotrophic fungi from arctic soils of Franz Joseph Land[END_REF][START_REF] Caretta | A record of Arthrobotrys tortor Jarowaja and Engyodontium album (Limber) de Hoog from Antarctica[END_REF][START_REF] Zucconi | Searching for eukaryotic life preserved in Antarctic permafrost[END_REF]. The lowest temperatures at which this fungus can grow seem to be around 4 or 5 °C, temperatures at which P. album developed in some cases but not in others [START_REF] Fernandes | Cold activity of Beauveria and Metarhizium, and thermotolerance of Beauveria[END_REF][START_REF] Jaouani | Diversity and enzymatic profiling of halotolerant micromycetes from Sebkha El Melah, a Saharan salt flat in southern Tunisia[END_REF]. The P. album samples that had not grown at low temperatures, germinated when temperatures were increased to 25 °C, suggesting that the fungus was inhibited at low temperatures without being killed. Parengyodontium album is generally not capable of growing at temperatures above 31 °C. The only exception is the strains belonging to subclade 2 of the three subclades defined by [START_REF] Tsang | Cutaneous hyalohyphomycosis due to Parengyodontium album gen. et comb[END_REF], which can grow at 35 °C. This temperature range for growth ranging from approximately 5 to 30 °C and the capacity of the fugus to survive at low temperatures make P. album a species that is well adapted to the environmental conditions of cultural heritage monuments. Notably, P. album survives on monuments subjected to cold winters, then grows when weather becomes milder [START_REF] Piotrowska | Abiotic determinants of the historical buildings biodeterioration in the former Auschwitz II -Birkenau concentration and extermination camp[END_REF], or grows in sites such as caves that remain relatively cool throughout the year [START_REF] Nováková | Microscopic fungi isolated from the Domica Cave system (Slovak Karst National Park, Slovakia). A review[END_REF].

Parengyodontium album: a species capable of feeding on various nutrient sources

As chemoorganotrophic organisms, P. album cannot develop without the presence of organic matter as a nutrient in the environment. For example, it has been proposed that P. album can feed on the organic pollutants in black crusts [START_REF] Sáiz-Jiménez | Biodeterioration vs biodegradation: the role of microorganisms in the removal of pollutants deposited on historic buidlings[END_REF]. Phototrophic organisms such as algae, cyanobacteria or lichens are generally considered as the primary colonizers in environments that are poor in nutrients, such as stone [START_REF] Dakal | Microbially induced deterioration of architectural heritages: routes and mechanisms involved[END_REF][START_REF] Scheerer | Microbial deterioration of stone monuments-an updated overview[END_REF][START_REF] Warscheid | Biodeterioration of stone: a review[END_REF]. The accumulation of the photosynthetic biomass created by the development of theses primary colonizers provides a suitable environment for the growth of heterotrophic organisms. Parengyodontium album appears to be one such recipient of this microbial succession [START_REF] Karpovich-Tate | Microbial communities on damaged frescoes and building materials in the cathedral of the nativity of the virgin in the Pafnutii-Borovskii monastery[END_REF], and is able to recolonize supports on remaining dead biofilms following UVc treatments [START_REF] Pfendler | Comparison of biocides, allelopathic substances and UV-C as treatments for biofilm proliferation on heritage monuments[END_REF].

Parengyodontium album has also been shown capable of feeding on products used in restoration of wall paintings. [START_REF] Cappitelli | The biodeterioration of synthetic resins used in conservation[END_REF] noted that the fungus could develop on several synthetic resins, and [START_REF] Sampo | A study of the fungi occurring on 15th century frescoes in Florence, Italy[END_REF] isolated a fungal species that probably belonged to P. album and was capable of growing on calcium caseinate and liquifying animal glue. Indeed, it is well known that P. album is an enzyme producer. It is used for the industrial production of proteinase K, which acts as serine endopeptidase and induces a keratin hydrolysis activity [START_REF] Ebeling | Proteinase K from Tritirachium album Limber[END_REF][START_REF] Jany | Amino acid sequence of proteinase K from the mold Tritirachium album Limber: Proteinase K-a subtilisin-related enzyme with disulfide bonds[END_REF]. The use of proteinase K produced by P. album to facilitate the hydrolysis of animal glue on paper artwork during a restoration process is somewhat ironic given the otherwise damaging effect of this fungus in the cultural heritage domain [START_REF] Micheli | Interdisciplinary approach to develop a disposable real time monitoring tool for the cleaning of graphic artworks. Application on "le Nozze di Psiche[END_REF]. This keratinolytic activity and the capacity of the fungus to produce cytotoxic polyketides led to the recognition of P. album as an emerging opportunistic pathogen [START_REF] Tsang | Cutaneous hyalohyphomycosis due to Parengyodontium album gen. et comb[END_REF]. The keratinolytic activity could also become an issue for the conservation of antique textiles [START_REF] Błyskal | Fungi utilizing keratinous substrates[END_REF]. Besides the production of protease, P. album has also been recognized as a producer of α-amylase, esterase, phosphatase lipase and chitinase [START_REF] Ali | Purification and characterization of extracellular, polyextremophilic α-amylase obtained from halophilic Engyodontium album[END_REF][START_REF] Jaouani | Diversity and enzymatic profiling of halotolerant micromycetes from Sebkha El Melah, a Saharan salt flat in southern Tunisia[END_REF][START_REF] Karpovich-Tate | Microbial communities on damaged frescoes and building materials in the cathedral of the nativity of the virgin in the Pafnutii-Borovskii monastery[END_REF]. A number of studies have shown these enzymes to be effective under high salinity conditions [START_REF] Ali | Purification and characterization of extracellular, polyextremophilic α-amylase obtained from halophilic Engyodontium album[END_REF][START_REF] Jaouani | Diversity and enzymatic profiling of halotolerant micromycetes from Sebkha El Melah, a Saharan salt flat in southern Tunisia[END_REF], which could explain the favourable development of P. album on monuments affected by salt crystallization.

The production of chitinase by P. album leads us to consider the entomogenous character of this fungus. The exoskeleton of arthropods is mainly composed of chitin [START_REF] Merzendorfer | Insect chitin synthases: a review[END_REF]. The role of arthropods in the dissemination of fungal species is commonly recognized, especially in environments where insects are numerous such as caves, catacombs and mural paintings [START_REF] Bastian | The impact of arthropods on fungal community structure in Lascaux Cave[END_REF][START_REF] Jurado | Entomogenous fungi and the conservation of the cultural heritage: A review[END_REF][START_REF] Trovão | Can arthropods act as vectors of fungal dispersion in heritage collections? A case study on the archive of the University of Coimbra, Portugal[END_REF]. Dead insects also provide a source of nutrients for entomogenous fungi in these nutrient-poor environments. It is well known that some of the successive fungal genera in which P. album has been classified contain entomogenous species, i.e. Beauveria and Engyodontium [START_REF] Samson | Atlas of entomopathogenic fungi[END_REF]. Indeed, Beauveria bassiana and B. brongnartii are used as commercial biological control agents against various pests [START_REF] Butt | Fungal biological control agents[END_REF], and Engyodontium parvisporum and E. geniculatum have been isolated from arthropods [START_REF] Gams | The hyphomycete genus Engyodontium a link between Verticillium and Aphanocladium[END_REF]. Several authors have linked the development of P. album on cultural heritage monuments to the presence of insects [START_REF] Gorbushina | Distribution of microorganisms on ancient wall paintings as related to associated faunal elements[END_REF][START_REF] Jurado | Entomogenous fungi and the conservation of the cultural heritage: A review[END_REF]Liñán et al., 2018;[START_REF] Nugari | Biodeterioration of mural paintings in a rocky habitat: The Crypt of the Original Sin (Matera, Italy)[END_REF][START_REF] Principi | Molecular studies of microbial community structure on stained pages of Leonardo da Vinci's Atlantic Codex[END_REF]. Although the association between P. album and arthropods has often been suggested rather than proved, the fungus has been isolated from spiders in at least three different studies [START_REF] Chandrashekhar | Occurrence of Beauveria alba on a spider[END_REF][START_REF] Martynenko | A hyphomycete, Engyodontium album (Limber) de Hoog, attacking spiders in underground headings of Kyiv-city[END_REF][START_REF] Trovão | Can arthropods act as vectors of fungal dispersion in heritage collections? A case study on the archive of the University of Coimbra, Portugal[END_REF]. Given that spiders are actually a preferred host for species belonging, or having belonged, to the Engyodontium genus [START_REF] Gams | The hyphomycete genus Engyodontium a link between Verticillium and Aphanocladium[END_REF], and in the knowledge that P. album is a chitinase producer, this association between arthropods and P. album is very likely.

Concluding remarks

The reviewing of multiple studies confirms that Parengyodontium album is a globally distributed environmental fungal species that can be found in extreme environments such as polar soils. In studies dealing specifically with cultural heritage, P. album was frequently isolated from deteriorated materials and from the environment of monuments, suggesting that the role played by this fungal species in the biodeterioration process may have been underestimated. The fungus was recovered from a wide range of supports including stone, wood, glass and paper, and was also found in monuments in an airborne form. The presence of P. album was marginal in some cases, but this species was dominant in samplings of other sites. The tolerance of P. album for salty environments could explain why it is often recovered from cultural heritage materials which often suffer from water infiltrations and from the crystallization of soluble salts. These environments are generally poor in nutrients, but P. album can feed on organic pollution, on biofilms composed of primary colonizers, and also probably on certain products used for restoration processes. Finally, it is likely that P. album is also capable of feeding on (dead) arthropods, and especially spiders, which are usually abundant in caves and catacombs, or on wall paintings. Arthropods could also be a means of dissemination for the fungus in these environments. The map shows the global distribution of P. album as well as the variety of environments from which the fungus has been isolated. The picture clearly shows the presence of a white veil due to P. album across almost the entire surface of the vault, with the exception of small areas where the colors are more intense.

Captions for Figures

  Fig. 2), which characterizes Tritirachium species. De Hoog (1978) created the genus Engyodontium and incorporated Beauveria alba under the name Engyodontium album (or Engyodontium albus). This change made the genus Beauveria more homogeneous by limiting it to species with dense clusters of short branches and fertile cells on undifferentiated hyphae, whereas Beauveria alba did not have a dense subverticillate to verticillate branching pattern. Finally, Tsang et al. (2016) found that Engyodontium album was phylogenetically and chemotaxonomically different to the three other species making up the genus Engyodontium and created the new genus Parengyodontium for the sole species Parengyodontium album. It was the first time that the species was renamed for other reasons than morphological features.

Figure 1 :

 1 Figure 1: Taxonomy of Parengyodontium album over time (graphics program: Inkscape).

Figure 2 :

 2 Figure 2: Macroscopic picture (recto and verso) of Parengyodontium album on Malt extract agar (MEA) (graphics program: Inkscape).

Figure 3 :

 3 Figure 3: Distribution of isolation sites cited in the review (graphics program: R).

Figure 4 :

 4 Figure 4: Wall paintings of the crypt of Saint-Savin-sur-Gartempe Abbey church, affected by

Acknowledgment

We thank Joanna Lignot for English language editing.

Lascaux cave, France [START_REF] Bastian | The impact of arthropods on fungal community structure in Lascaux Cave[END_REF][START_REF] Bastian | The microbiology of Lascaux cave[END_REF] Chapel of Herberstein Castle, Austria [START_REF] Berner | A comparative study of the fungal flora present in medieval wall paintings in the chapel of the castle Herberstein and in the parish church of St Georgen in Styria, Austria[END_REF] National Museum of Fine Arts, Cuba [START_REF] Borrego | Fungal assessment on storerooms indoor environment in the National Museum of Fine Arts, Cuba[END_REF] Crypt of Kodersdorf parish church, Germany [START_REF] Gorbushina | Distribution of microorganisms on ancient wall paintings as related to associated faunal elements[END_REF] St. Peter and Paul church, Koenigslutter, Germany [START_REF] Gorbushina | Distribution of microorganisms on ancient wall paintings as related to associated faunal elements[END_REF] St. Martin's church, Kreiensen-Greene, Germany [START_REF] Gorbushina | Distribution of microorganisms on ancient wall paintings as related to associated faunal elements[END_REF] Canterbury Cathedral, England [START_REF] Jeffries | Growth of Beauvaria alba on mural paintings in Canterbury Cathedral[END_REF] Cathedral of the Nativity of the Virgin, Pafnutii-Borovskii monastery, Russia (Karpovich-Tate and Rebrikova, 1991)

Concentration camp of Auschwitz II -Birkenau, Poland [START_REF] Koziróg | Colonising organisms as a biodegradation factor affecting historical wood materials at the former concentration camp of Auschwitz II -Birkenau[END_REF][START_REF] Piotrowska | Abiotic determinants of the historical buildings biodeterioration in the former Auschwitz II -Birkenau concentration and extermination camp[END_REF] "An der Strangriede" cemetery in Hannover, Germany [START_REF] Krumbein | Biological aspects of deterioration and consolidation of selected tombstones on Jewish cemeteries, 8th International Congress on Deterioration and Conservation of Stone[END_REF] Laugerie-Haute shelter, France [START_REF] Lepinay | Biofilm communities survey at the areas of salt crystallization on the walls of a decorated shelter listed at UNESCO World cultural Heritage[END_REF] Crypt of Saint-Savin-sur-Gartempe Abbey church, France [START_REF] Leplat | White fungal covering on the wall paintings of the Saint-Savin-sur-Gartempe Abbey church crypt: A case study[END_REF] Points cave, France [START_REF] Leplat | Aerobiological behavior of Paleolithic decorated caves: a comparative study of five caves in the Gard department (France)[END_REF] Latrone cave, France [START_REF] Leplat | Aerobiological behavior of Paleolithic decorated caves: a comparative study of five caves in the Gard department (France)[END_REF] Bayol cave, France [START_REF] Leplat | Aerobiological behavior of Paleolithic decorated caves: a comparative study of five caves in the Gard department (France)[END_REF] Narja cave, Spain (Liñán et al., 2018) Zbrašov aragonite caves, Czech Republic [START_REF] Marvanová | Microscopic fungi in the Zbrašov aragonite caves[END_REF] Biblioteca di area umanistica (BAUM), Italy [START_REF] Micheluz | The effects of book disinfection to the airborne microbiological community in a library environment[END_REF] Sorcerer's cave, France [START_REF] Mihajlovski | Characterization of the archaeal and fungal diversity associated with gypsum efflorescences on the walls of the decorated Sorcerer's prehistoric cave[END_REF] Domica cave, Slovak Republic [START_REF] Nováková | Microscopic fungi isolated from the Domica Cave system (Slovak Karst National Park, Slovakia). A review[END_REF] Crypt of the Original Sin, Italy [START_REF] Nugari | Biodeterioration of mural paintings in a rocky habitat: The Crypt of the Original Sin (Matera, Italy)[END_REF] Humberstone and Santa Laura saltpeter works, Chile [START_REF] Ortiz | Deterioration, decay and identification of fungi isolated from wooden structures at the Humberstone and Santa Laura saltpeter works: a world heritage site in Chile[END_REF] Church of Vicherey, France [START_REF] Pfendler | Comparison of biocides, allelopathic substances and UV-C as treatments for biofilm proliferation on heritage monuments[END_REF] Staircase of Hallstatt, Austria [START_REF] Piñar | Biodeterioration risk threatens the 3100 year old staircase of Hallstatt (Austria): Possible involvement of halophilic microorganisms[END_REF] Church of Boris and Gleb, Russia [START_REF] Ponizovskaya | Micromycetes as colonizers of mineral building materials in historic monuments and museums[END_REF] Kuskovo manor, Russia [START_REF] Ponizovskaya | Micromycetes as colonizers of mineral building materials in historic monuments and museums[END_REF] The State Tretyakov Gallery archive, Russia [START_REF] Ponizovskaya | Micromycetes as colonizers of mineral building materials in historic monuments and museums[END_REF] Leonardo da Vinci's Atlantic Codex, Italy [START_REF] Principi | Molecular studies of microbial community structure on stained pages of Leonardo da Vinci's Atlantic Codex[END_REF] Roman catacombs of St. Domitilla, Italy [START_REF] Saarela | Heterotrophic microorganisms in air and biofilm samples from Roman catacombs, with special emphasis on actinobacteria and fungi[END_REF] Mechelen Cathedral, Belgium (Saiz-Jimenez, 1993) Monastery of Santa María de la Rábida, Spain (Sáiz-Jiménez and [START_REF] Sáiz-Jiménez | Microorganisms and environmental pollution as deteriorating agents of the frescoes of the Monastery of "Santa María de la Rábida[END_REF] Ognissanti church, Italy [START_REF] Sampo | A study of the fungi occurring on 15th century frescoes in Florence, Italy[END_REF] Church of Stockkämpfen, Germany [START_REF] Schabereiter-Gurtner | Analysis of fungal communities on historical church window glass by denaturing gradient gel electrophoresis and phylogenetic 18S rDNA sequence analysis[END_REF] Historical building from 17 th century, Slovak Republic [START_REF] Simonovicova | Engyodontium album, a new species of microscopic fungi for Slovakia and its keratinolytic activity[END_REF] Necropolis of Tarquinia, Italy [START_REF] Sprocati | A microbiological survey of the Etruscan Mercareccia tomb (Italy): contribution of microorganisms to deterioration and restoration[END_REF] Archive of the University of Coimbra, Portugal [START_REF] Trovão | Can arthropods act as vectors of fungal dispersion in heritage collections? A case study on the archive of the University of Coimbra, Portugal[END_REF] Kartchner caverns, USA [START_REF] Vaughan | Fungal communities on speleothem surfaces in Kartchner Caverns, Arizona, USA[END_REF]) Grey boxes indicate the type of material from which Parengyodontium album has been isolated 547