Karine Alain
email: karine.alain@univ-brest.fr

Nolwenn Callac

Marianne Guégan

Françoise Lesongeur

Philippe Crassous

Marie-Anne Cambon-Bonavita

Joël Querellou

Daniel Prieur

Nautilia abyssi sp. nov., a thermophilic, chemolithoautotrophic, sulfur-reducing bacterium isolated from an East Pacific Rise hydrothermal vent

Keywords:

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

chemolithoautotrophically with H 2 as an energy source, S° as an electron acceptor and CO 2 as a carbon source. Alternatively, strain PH1209 T was able to use peptone and yeast extract as carbon sources. The G+C content of the genomic DNA was 35 mol%.

Phylogenetic analyses based on 16S rRNA gene sequencing showed that strain PH1209 T fell within the order Nautiliales, in the class Epsilonproteobacteria. Comparative 16S rRNA gene sequence analysis indicated that strain PH1209 T belonged to the genus Nautilia, and shared, respectively, 97.2 and 98.7% 16S rRNA gene sequence identity with Nautilia lithotrophica and Nautilia profundicola. It is proposed, from the polyphasic evidence, that the strain should be placed into a novel species, Nautilia abyssi sp. nov. The type strain is PH1209 T (= DSM 21157 T = JCM 15390 T ).

Epsilonproteobacteria are widely distributed in marine and terrestrial ecosystems [START_REF] Campbell | The versatile ε-proteobacteria: key players in sulphidic habitats[END_REF].

They are particularly common and abundant in 30-70°C areas of deep sea hydrothermal vents, as indicated by their prevalence in the clone libraries [START_REF] Polz | Dominance of one bacterial phylotype at a Mid-Atlantic Ridge hydrothermal vent site[END_REF][START_REF] Longnecker | Expansion of the geographic distribution of a novel lineage of epsilon-Proteobacteria to a hydrothermal vent site on the Southern East Pacific Rise[END_REF][START_REF] Lopez-Garcia | Wide bacterial diversity associated with tubes of the vent worm Riftia pachyptila[END_REF][START_REF] Alain | Early steps in microbial colonization processes at deep-sea hydrothermal vents[END_REF], the results of fluorescence in situ hybridization [START_REF] Moussard | Novel uncultured Epsilonproteobacteria dominate a filamentous sulphur mat from the 13°N hydrothermal vent field, East Pacific Rise[END_REF] and the isolation of several representatives [START_REF] Alain | Caminibacter hydrogeniphilus gen. nov., sp. nov., a novel thermophilic, hydrogen-oxidizing bacterium isolated from an East Pacific Rise hydrothermal vent[END_REF][START_REF] Miroshnichenko | Nautilia lithotrophica gen. nov., sp. nov., a thermophilic sulfur-reducing εproteobacterium isolated from a deep-sea hydrothermal vent[END_REF][START_REF] Takai | Isolation and phylogenetic diversity of members of previously uncultivated ε-Proteobacteria in deep-sea hydrothermal fields[END_REF][START_REF] Takai | Isolation and phylogenetic diversity of members of previously uncultivated ε-Proteobacteria in deep-sea hydrothermal fields[END_REF][START_REF] Takai | Lebetimonas acidiphila gen. nov., sp. nov., a novel thermophilic, acidophilic, hydrogen-oxidizing chemolithoautotroph within the 'Epsilonproteobacteria', isolated from a deep-sea hydrothermal fumarole in the Mariana Arc[END_REF][START_REF] Takai | Sulfurimonas paralvinellae sp. nov., a novel mesophilic, hydrogen-and sulfur-oxidizing chemolithoautotroph within the Epsilonproteobacteria isolated from a deep-sea hydrothermal vent polychaete nest, reclassification of Thiomicrospira denitrificans comb. nov. and emended description of the genus Sulfurimonas[END_REF][START_REF] Voordeckers | Caminibacter mediatlanticus sp. nov., a thermophilic, chemolithoautotrophic, nitrate-ammonifying bacterium isolated from a deep-sea hydrothermal vent on the Mid-Atlantic Ridge[END_REF]. Within this singular ecosystem, Epsilonproteobacteria are retrieved in various habitats, thriving (i) as free-living organisms on chimney structures, within vent plumes and in sediments, (ii) as epi-or endosymbionts of hydrothermal invertebrates, or (iii) embedded in mats on the surfaces of chimney rocks or animals. Cultured isolates from deep-sea vents are all mesophilic to thermophilic chemolithoautotrophs coupling the oxidation of hydrogen or sulfur compounds to the reduction of nitrate, sulfur compounds or oxygen [START_REF] Takai | Isolation and phylogenetic diversity of members of previously uncultivated ε-Proteobacteria in deep-sea hydrothermal fields[END_REF][START_REF] Campbell | The versatile ε-proteobacteria: key players in sulphidic habitats[END_REF]. Because of their abundance and metabolic abilities, Epsilonproteobacteria are likely to be key players of the carbon, sulfur and nitrogen biogeochemical cycling at deep-sea vents. Two orders are currently described within the class Epsilonproteobacteria Garrity et al. 2006(Validation List n°107, Garrity et al., 2005), namely the Nautiliales [START_REF] Miroshnichenko | Caminibacter profundus sp. nov., a novel thermophile of Nautiliales ord. nov. within the class 'Epsilonproteobacteria' isolated from a deep-sea hydrothermal vent[END_REF] and the Campylobacterales Garrity et al. 2006(Validation List n°107, Garrity et al., 2005). The order Nautiliales comprises the genera Nautilia [START_REF] Miroshnichenko | Nautilia lithotrophica gen. nov., sp. nov., a thermophilic sulfur-reducing εproteobacterium isolated from a deep-sea hydrothermal vent[END_REF], Caminibacter [START_REF] Alain | Caminibacter hydrogeniphilus gen. nov., sp. nov., a novel thermophilic, hydrogen-oxidizing bacterium isolated from an East Pacific Rise hydrothermal vent[END_REF] and Lebetimonas [START_REF] Takai | Lebetimonas acidiphila gen. nov., sp. nov., a novel thermophilic, acidophilic, hydrogen-oxidizing chemolithoautotroph within the 'Epsilonproteobacteria', isolated from a deep-sea hydrothermal fumarole in the Mariana Arc[END_REF] which are exclusively composed of thermophilic strains isolated from deep-sea hydrothermal vents and which have been found in association with invertebrates or with chimney edifices. At present, the genus Nautilia is composed of two species, Nautilia lithotrophica [START_REF] Miroshnichenko | Nautilia lithotrophica gen. nov., sp. nov., a thermophilic sulfur-reducing εproteobacterium isolated from a deep-sea hydrothermal vent[END_REF] and Nautilia profundicola [START_REF] Smith | Nautilia profundicola sp. nov., a thermophilic, sulfur-reducing epsilonproteobacterium from deep-sea hydrothermal vents[END_REF]. Both strains are strictly anaerobic sulfurreducing mixotrophs able to grow on hydrogen and carbon dioxide, or alternatively on formate.

In this study, a novel marine bacterium belonging to the genus Nautilia is described. Based on the results of a polyphasic taxonomic analysis, the strain PH1209 T represents a novel species, Nautilia abyssi sp. nov.

In April-May 2002, during the PHARE oceanographic cruise, fragments of active hydrothermal chimney rocks covered with colonies of the tubeworm polychaete Alvinella spp. were collected from 2620m depth at the Elsa vent field, on the East Pacific Rise 13°N (12°48'N, 103°56'W). Sample collection, subsampling and storage procedures were as described elsewhere [START_REF] Alain | Early steps in microbial colonization processes at deep-sea hydrothermal vents[END_REF]. One subsample collected on the Ph01 chimney was used to inoculate series of media, including KA22 medium [START_REF] Alain | Caminibacter hydrogeniphilus gen. nov., sp. nov., a novel thermophilic, hydrogen-oxidizing bacterium isolated from an East Pacific Rise hydrothermal vent[END_REF], and incubated at 60°C under a gas phase of H 2 /CO 2 (80/20; 200 kPa). After 24h incubation, dense populations of short, rod-shaped, motile cells were observed and purified by repeated dilution to extinction series. One isolate, referenced as strain PH1209 T , is described in this publication. Purity of this isolate was confirmed routinely by microscopic examination and by repeated partial sequencing of the 16S rRNA gene using several primers. Stock cultures were stored at ─80°C in KA22 medium supplemented with 5% (v/v) DMSO.

Morphological characteristics of the cells were determined by light microscopy (Olympus CX40) and by scanning electron microscopy (FEI Quanta 200). Cells of strain PH1209 T were Gram-negative, straight rods of 1.05-2.21 µm in length (mean 1.63µm ± 0.34, n=11) and 0.30-0.51 µm in width (mean 0.39 ± 0.05, n=11) in the mid-exponential phase of growth (see Supplementary Fig. S1 in IJSEM online). They occurred mainly singly and were highly motile by a polar flagellum (Fig. S1A). Division was by constriction (Fig. S1B).

Formation of spores was never observed.

The physiological characterization of the novel isolate was carried out in a basal medium referenced as "NPKsalts" and containing (per liter): 0.33 g NH 4 Cl, 0.33 g KCl, 0.33 g CaCl 2 .2H 2 O, 0.33 g MgCl 2 .6H 2 O, 25 g NaCl, 1.0 g NaNO 3 , 1.95 g MES buffer (Sigma) and 1 mg resazurin (Sigma). Its pH was adjusted to 6.0. Once prepared, this medium was autoclaved and then cooled to room temperature under a stream of O 2free N 2 gas. Concentrated anaerobic filter-sterilized solutions of vitamins and trace elements were added to the medium after autoclaving. Then, just before inoculation, Na 2 S.9H 2 O, KH 2 PO 4 and elemental sulfur were provided from sterile stocks, to final concentrations of 0.04% (w/v), 20 mM and 1.2% (w/v), respectively.

Unless stated otherwise, the experiments were carried out anaerobically, under a gas phase of H 2 /CO 2 (80/20; 200 kPa), and incubation were done in the dark and under agitation. Growth was routinely monitored by direct cell counting using a modified Thoma chamber (depth 10 µm), or by counting after fixation with 1% (v/v) glutaraldehyde and storage at -20°C. Growth rates were calculated using linear regression analysis of four to nine points along the logarithmic portions of the resulting growth curves. The determination of the temperature range for growth was tested over the range 30-80°C (i.e. 30, 33, 37, 45, 50, 55, 60, 65, 70, 75, 80°C). No growth was observed at 30°C, 70°C and above. The novel isolate grew from 33 to 65°C, with an optimum growth rate at 60°C (see Supplementary Fig. S2A in IJSEM online). The pH range for growth was tested at 60°C in basal medium buffered and adjusted to the required initial pH as described elsewhere [START_REF] Alain | Caminibacter hydrogeniphilus gen. nov., sp. nov., a novel thermophilic, hydrogen-oxidizing bacterium isolated from an East Pacific Rise hydrothermal vent[END_REF]. Growth was observed from pH 5.0 to pH 8.0, the optimum being around pH 6.0-6.5 (Fig. S2B). No growth was observed at pH 4.0 and pH 8.5. Salt tolerance was tested at 60°C in NPKsalts medium prepared with various concentrations of NaCl (0, 0.5, 1, 2, 3, 4, 5, 6, 8 and 10% w/v). Growth was observed at salt concentrations ranging from 2 to 4% (w/v) NaCl, the optimum salinity being around 3% (Fig. S2C). No growth was observed at 1 and 5% (w/v) NaCl. Under optimal growth conditions, the generation time of strain PH1209 T was around 120 minutes.

Strain PH1209 T was a strictly anaerobic, chemolithoautotrophic bacterium that used sulfur, hydrogen and carbon dioxide as respective primary electron acceptor, electron donor and carbon source. Its ability to use alternative electron acceptors was tested by adding colloidal sulfur (Sigma Aldrich) (5 g l -1 ), L-cystine (12 g l -1 ), sulfite (1 mM), thiosulfate (20 mM), sulfate (20 mM), nitrate (10 mM), nitrite (1 mM) and oxygen (1% v/v) to nitrate and sulfur-depleted media, under an atmosphere of H 2 /CO 2 (80/20; 200 kPa). Quantitative determination of hydrogen sulfide was as described elsewhere [START_REF] Cord-Ruwisch | A quick method for the determination of dissolved and precipitated sulfides in cultures of sulphate-reducing bacteria[END_REF]. The novel isolate was found to grow with elemental sulfur and colloidal sulfur, with concomitant production of H 2 S, but did not grow when L-cystine, sulfite, thiosulfate, sulfate, nitrate, nitrite and oxygen were used as electron acceptors.

To examine possible carbon sources other than CO 2 , a variety of organic carbon sources were tested in the presence of sulfur, under an atmosphere of H 2 100% (200 kPa). Formate (10 mM), acetate (10 mM), butyrate (10 mM), propionate (10 mM), methanol (0.5% v/v), pyruvate (10 mM), lactate (0.5% v/v), fumarate (10 mM), glucose (10 mM), peptone (2 g l -1 ) and yeast extract (2 g l -1 ) were tested as potential substrates. Heterotrophic growth (with concomitant H 2 S production) was observed exclusively with yeast extract and peptone and was probably the result of the decarboxylation of amino acids. The growth rates with yeast extract and peptone were in the same order of magnitude than the one measured with carbon dioxide as carbon source. To test for the capability of the strain to use electron donors other than molecular hydrogen, the strain was cultivated under a gas phase of N 2 /CO 2 (80/20, 200 kPa) in the presence of formate (20 mM), acetate (20 mM), methanol 0.5% (v/v) and yeast extract (2 g l -1 ), and with sulfur as a terminal electron acceptor. No growth was observed with the alternative energy sources, indicating that strain PH1209 T was a strict hydrogen-oxidizer. The nitrogen sources for growth were also examined in a nitrogendepleted medium. The novel isolate was found to grow on organic and inorganic nitrogen sources.

Significant growth was observed when NH 4 Cl (20 mM), glutamate (10 mM), yeast extract (0.2 g l -1 ), tryptone (0.2 g l -1 ), gelatin (0.05% v/v) and urea (0.05% v/v) were provided as sole nitrogen source.

Antibiotic resistance was tested in the presence of a variety of antibiotics from different chemical nature and with different targets and mechanisms. The resistance to vancomycin, streptomycin, chloramphenicol, kanamycin, rifampicin, penicillin, ampicillin and tetracycline was investigated at concentrations of 10, 25, 50 and 100 µg ml -1 . When the antibiotic was diluted in ethanol (chloramphenicol) or DMSO (rifampicin), the same volume of solvent was added to control cultures. All antibiotics were added aseptically before inoculation and the cultures were incubated at 60°C for one week. Strain PH1209 T was found to be sensitive to vancomycin, streptomycin, chloramphenicol, penicillin, ampicillin and tetracycline, all at 10 µg ml -1 . It grew in the presence of 10 µg ml -1 rifampicin and 25 µg ml -1 kanamycin, but was sensitive to higher concentrations of these two antibiotics.

The genomic DNA G+C content was determined, by the Identification Service of the DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany), by HPLC analysis of deoxyribonucleosides as described by [START_REF] Mesbah | Precise measurement of the G+C content of deoxyribonucleic acid by high performance liquid chromatography[END_REF]. The G+C content of strain PH1209 T was 35 mol%.

The almost complete 16S rRNA gene (1369 bp) of the strain was double-strand sequenced, as described elsewhere [START_REF] Alain | Caminibacter hydrogeniphilus gen. nov., sp. nov., a novel thermophilic, hydrogen-oxidizing bacterium isolated from an East Pacific Rise hydrothermal vent[END_REF]. This sequence was compared to those in available databases by use of the BLAST program [START_REF] Altschul | Basic local alignment search tool[END_REF] and then aligned to its nearest neighbours using the CLUSTALX program [START_REF] Thompson | The ClustalX windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools[END_REF]. Alignments were refined manually using the SEAVIEW program [START_REF] Galtier | SEAVIEW and PHYLO_WIN: two graphic tools for sequence alignment and molecular phylogeny[END_REF]. Distance matrixes were calculated with the Lasergene 6 version software. Phylogenetic trees were constructed by the PHYLIP (PHYlogeny Inference Package) version 3.63 software (http://evolution.genetics.washington.edu/phylip/getme.html) on the basis of evolutionary distance (neighbour-joining method with Jukes and Cantor corrections) [START_REF] Saitou | The neighbour-joining method: a new method for reconstructing phylogenetic trees[END_REF] and maximum likelihood [START_REF] Felsenstein | Evolutionary trees from DNA sequences: a maximum likelihood approach[END_REF]. The robustness of the inferred topologies was assessed by bootstrap analyses based on 1000 bootstrap resamplings for the neighbour-joining and 100 replications for the maximum likelihood method [START_REF] Felsenstein | Confidence limits on phylogenies: an approach using the bootstrap[END_REF]. Comparison of the 16S rRNA gene sequence with sequences of Bacteria indicated that the novel isolate belonged to the class Epsilonproteobacteria Garrity et al. 2006(Validation List n°107, Garrity et al., 2005) and more especially to the order Nautiliales [START_REF] Miroshnichenko | Caminibacter profundus sp. nov., a novel thermophile of Nautiliales ord. nov. within the class 'Epsilonproteobacteria' isolated from a deep-sea hydrothermal vent[END_REF]. Within this lineage that is composed exclusively of taxa from deep-sea hydrothermal vents, the novel isolate was found to be most closely related to a group of moderately thermophilic sulfur reducers, all isolated from the EPR 13°N like PH1209 T (Fig. 1). The novel isolate shared 98.7% 16S rRNA gene sequence identity with Nautilia profundicola strain AmH T [START_REF] Smith | Nautilia profundicola sp. nov., a thermophilic, sulfur-reducing epsilonproteobacterium from deep-sea hydrothermal vents[END_REF], 97.2% 16S rRNA gene sequence identity with Nautilia lithotrophica strain 525 T [START_REF] Miroshnichenko | Nautilia lithotrophica gen. nov., sp. nov., a thermophilic sulfur-reducing εproteobacterium isolated from a deep-sea hydrothermal vent[END_REF] and 97.4% 16S rRNA gene sequence identity with strain Ex-18.2, a third isolate not formerly described [START_REF] Campbell | Growth and phylogenetic properties of novel bacteria belonging to the epsilon subdivision of the Proteobacteria enriched from Alvinella pompejana and deep-sea hydrothermal vents[END_REF]. These three closest relatives were all isolated from tubes of the worm Alvinella pompejana and belonged to the genus Nautilia. Otherwise, the novel isolate was most distantly related to members of the genera Lebetimonas and Caminibacter, sharing 91.9% to 93.2% 16S rRNA gene sequence identity with representative species of these genera (Table 1). Based on the sequence similarity and phylogenetic analyses, the novel isolate could be assigned to the genus Nautilia. The level of 16S rDNA sequence dissimilarity with N. profundicola and N. lithotrophica suggests that the novel isolate belongs to a novel species [START_REF] Stackebrandt | Taxonomic parameters revisited: tarnished gold standards[END_REF].

The phenotypic and genotypic properties of the novel isolate described herein generally met the minimal characteristics described for the order Nautiliales [START_REF] Miroshnichenko | Caminibacter profundus sp. nov., a novel thermophile of Nautiliales ord. nov. within the class 'Epsilonproteobacteria' isolated from a deep-sea hydrothermal vent[END_REF]. Indeed, strain PH1209 T is a marine thermophilic sulfur-reducing bacterium growing chemolithoautrophically from H 2 oxidation. It unambiguously branches with other Nautiliales. Nevertheless, strain PH1209 T can be easily distinguished from other Nautiliales species in terms of a number of phylogenetic, genotypic and physiological features.

These distinctive criteria are detailed in Table 1. In brief, in addition to the phylogenetic distance, the novel taxon differs from its closest relatives by its temperature, NaCl and pH ranges for growth. Its generation time under optimal growth condition is also slightly different from the ones of its relatives. Furthermore, differences in the utilization profiles of carbon sources, electron donors and electron acceptors are also observed. In contrast to its congeners N. lithotrophica and N. profundicola which are able to use formate as energy and carbon source, the novel isolate is unable. Finally, another distinctive criterion is the DNA G+C content. In conclusion, in view of all the above-mentioned distinctive features, we propose that the isolate PH1209 T should be assigned as the type strain of a novel species, for which the name Nautilia abyssi sp.

nov. is proposed.

Description of Nautilia abyssi sp. nov.

Nautilia abyssi (a.bys'si. L. gen. n. abyssi, of an abyss, of the great deep).

Cells are Gram-negative motile rods, approximately 1.6 µm in length and 0.4 µm in width, with a single polar flagellum.

Optimal growth occurs at 60°C, with a growth range from 33 to 65°C. The pH and NaCl ranges are 5.0-8.0 (optimum 6.0-6.5) and 2-4% (w/v) (optimum, 3% w/v NaCl), respectively. Growth occurs under strictly anaerobic conditions using H 2 as an electron donor, elemental sulfur (or colloidal sulfur) as a terminal electron acceptor and CO 2 as a carbon source. Yeast extract and peptone can be used as alternative carbon sources, but formate, acetate, methanol, lactate, propionate, fumarate, malate, citrate, pyruvate, glucose and glycogen can not. The following are not utilized as electron acceptors: L-cystine, thiosulfate, sulfate, sulfite, nitrate, nitrite, oxygen. The following are not used as electron donors:

formate, acetate, methanol and yeast extract. Sensitive to 10 µg ml -1 of the following antibiotics: vancomycin, streptomycin, chloramphenicol, penicillin, ampicillin, tetracycline; sensitive to 25 µg ml -1 rifampicin and 50 µg ml -1 kanamycin. Genomic DNA G+C content of the type strain PH1209 T is 35 mol%.

The type strain, PH1209 T (DSM 21157 T , JCM 15390 T ) was isolated from the walls of an active deep-sea hydrothermal chimney colonized with alvinellid worms, on the East Pacific Rise (103°56'W, 12°48'N). It is also available under request at the "Souchothèque de Bretagne" (catalogue LMBE) culture collection (http://www.ifremer.fr/souchotheque/). Table 1. Characteristics differentiating strain PH1209 T from related species of the order Nautiliales.

TABLES and FIGURES

Species: 1, Nautilia abyssi PH1209 T (this study); 2, Nautilia profundicola AmH T [START_REF] Smith | Nautilia profundicola sp. nov., a thermophilic, sulfur-reducing epsilonproteobacterium from deep-sea hydrothermal vents[END_REF]; 3, Nautilia lithotrophica 525 T [START_REF] Miroshnichenko | Nautilia lithotrophica gen. nov., sp. nov., a thermophilic sulfur-reducing εproteobacterium isolated from a deep-sea hydrothermal vent[END_REF]; 4, Caminibacter hydrogeniphilus AM1116 T [START_REF] Alain | Caminibacter hydrogeniphilus gen. nov., sp. nov., a novel thermophilic, hydrogen-oxidizing bacterium isolated from an East Pacific Rise hydrothermal vent[END_REF]; 5, Caminibacter profundus CR T [START_REF] Miroshnichenko | Caminibacter profundus sp. nov., a novel thermophile of Nautiliales ord. nov. within the class 'Epsilonproteobacteria' isolated from a deep-sea hydrothermal vent[END_REF]; 6, Caminibacter mediatlanticus TB-2 T [START_REF] Voordeckers | Caminibacter mediatlanticus sp. nov., a thermophilic, chemolithoautotrophic, nitrate-ammonifying bacterium isolated from a deep-sea hydrothermal vent on the Mid-Atlantic Ridge[END_REF]; 7, Lebetimonas acidiphila Pd55 T [START_REF] Takai | Lebetimonas acidiphila gen. nov., sp. nov., a novel thermophilic, acidophilic, hydrogen-oxidizing chemolithoautotroph within the 'Epsilonproteobacteria', isolated from a deep-sea hydrothermal fumarole in the Mariana Arc[END_REF].

Legend: +, positive; ─, negative; w, weak growth; ND, not determined. The percentage of 16S rRNA gene sequence identity is calculated in reference to the 16S rRNA gene sequence of the novel isolate PH1209 T .

Fig. 1 .

 1 Fig. 1. Phylogenetic tree based on 16S rRNA gene sequences of strain PH1209 T and representative members of related genera within the class Epsilonproteobacteria. Sequence data of reference strains were obtained from the GenBank/EMBL and/or RDP databases. Two species from the Gammaproteobacteria were chosen as outgroups. Accession numbers are indicated in parentheses. The topology shown corresponds to an unrooted tree obtained by the maximum likelihood algorithm, established using the PHYLIP package. Bootstrap values (from 100 replicates) are indicated at the branch nodes. The positioning of the novel isolate was confirmed by the neighbour-joining method. The scale bar indicates 2 nt substitutions per 100 nt.

  Fig. S1. Scanning electron micrographs of cells of strain PH1209 T in the mid-exponential phase of growth, showing the polar flagellum (A) and division by constriction (B). Bar, 1.0 µm.

ACKNOWLEDGEMENTS

We acknowledge Prof. J. P. Euzéby for support in the Latin etymologies of the species name. We thank the captain and crew of the NO L'Atalante, the pilots and support crew of the ROV Victor and N. Le Bris, Chief Scientist for helping us to collect deep-sea hydrothermal vent samples during the PHARE oceanographic cruise. We are grateful to the anonymous reviewers for their constructive comments about the manuscript.

This work was financially supported by the Région Bretagne and the joined research unit UMR6197, linking the Université de Bretagne Occidentale to the Ifremer and the Centre National de la Recherche Scientifique.

The GenBank/EMBL/DDBJ


How Sustainability Ratings Might Deter "Greenwashing": A Closer Look at Ethical Corporate Communication

Keywords: ethical corporate marketing, CSR communication, attribution theory, sustainability ratings

Of the many ethical corporate marketing practices, many firms use corporate social responsibility (CSR) communication to enhance their corporate image. Yet consumers, overwhelmed by these more or less well-founded CSR claims often have trouble identifying truly responsible firms. This confusion encourages "greenwashing" and may make CSR initiatives less effective. On the basis of attribution theory, this study investigates the role of independent sustainability ratings on consumers' responses to companies' CSR communication. Experimental results indicate the negative effect of a poor sustainability rating for corporate brand evaluations in the case of CSR communication, because consumers infer less intrinsic motives by the brand. Sustainability ratings thus could act to deter "greenwashing" and encourage virtuous firms to persevere in their CSR practices.

INTRODUCTION

Broadly defined, corporate social responsibility (CSR) attempts to achieve commercial success in ways that honour ethical values and respect people, communities, and the natural environment (Bhattacharya and Sen, 2004). The study of CSR generally appears within investigations of general stakeholder theory [START_REF] Clarkson | A stakeholder framework for analyzing and evaluating corporate social performance[END_REF][START_REF] Donaldson | The stakeholder theory of the corporation: concepts, evidence, and implications[END_REF], but consumers largely were ignored as stakeholders before marketing researchers started to examine their responses to firms' respect or violation of social principles. Beyond consumers' responses to CSR activities, the question of their reactions to ethical corporate marketing and, more specifically, to CSR communication, though relatively recent in marketing research [START_REF] Maignan | Corporate social responsibility and marketing: an integrative framework[END_REF][START_REF] Swaen | The use of corporate social responsibility arguments in communication campaigns: does source credibility matter?[END_REF][START_REF] Morsing | Corporate social responsibility as strategic auto-communication: on the role of external stakeholders for member identification[END_REF][START_REF] Du | Maximizing business returns to Corporate Social Responsibility (CSR): the role of CSR communication[END_REF], has gained greater importance, because CSR communication expenses have grown to become the third-largest budget item for corporate communication departments in large companies [START_REF] Hutton | Reputation management: the new face of corporate public relations?[END_REF].

CSR corporate communication pertains to communicated corporate identity and is supposed to play a crucial role in the formation of ethical corporate perceptions (Balmer et al., 2007;[START_REF] Fukukawa | Mapping the interface between corporate identity, ethics and corporate responsibility[END_REF], and social legitimacy [START_REF] Waeraas | Green legitimation: the construction of an environmental ethos[END_REF][START_REF] Vanhamme | Too good to be true! The effectiveness of CSR history in countering negative publicity[END_REF]. However, the profusion of CSR claims, whether well-founded or not, creates difficulties for consumers who attempt to distinguish between truly virtuous firms and firms taking opportunistic advantage of sustainable development trends or, otherwise stated, between reputation and rhetoric [START_REF] Fukukawa | Mapping the interface between corporate identity, ethics and corporate responsibility[END_REF]Bernstein, 2009). In response, a strong movement denounces "greenwashing" (Bradford, 2007), defined as tactics that mislead "consumers regarding the environmental practices of a company or the environmental benefits of a product or service" (www.terrachoice.com). In such conditions, the potential benefits of CSR communication for corporate brand evaluation may be questionable, even for truly responsible companies. The situation also could lead to a prisoner's dilemma, in which responsible firms would benefit if they halted their responsible practices but still communicated about those practices. This dilemma raises an important societal research question: How can society regulate CSR communication practices to deter "greenwashing" and encourage virtuous companies in their initiatives?

Within the context of a growing number of independent sources of information, this research specifically addresses questions about the potential influence of sustainability ratings on consumers' responses to CSR communication. To reach this objective, we investigate how consumers decode CSR communication in light of sustainability ratings, for which attribution theory offers a particularly well-suited option [START_REF] Sjovall | From actions to impressions: cognitive attribution theory and the formation of corporate reputation[END_REF][START_REF] Van De Ven | An ethical framework for the marketing of corporate social responsibility[END_REF]). In the next section, we therefore summarise important concepts from ethical corporate marketing literature, with particular attention to distinguishing controllable corporate communication from non-controllable corporate information. Then we draw on attribution theory to derive hypotheses about how a good or poor sustainability rating might influence consumers' attitude making process and CSR communication's efficiency through motive attributions. To test the hypotheses, we turn to an experiment with a sample of adult consumers. We conclude with a discussion of the theoretical and societal implications of our findings for sustainability ratings and the effects of CSR communication on corporate brand building.

LITERATURE REVIEW

CSR communication and ethical corporate marketing

To clarify the corporate marketing paradigm, Balmer andGreyser (2003, 2007) propose an integrative model of corporate identity composed of five distinct facets. The communicated identity facet-or what the company communicates to its shareholders-has particular importance for this research, because communicated identity serves as a nexus between the company's identity and image [START_REF] Gray | Managing corporate image and corporate reputation[END_REF], which reflects the "immediate mental picture an individual has of an organization" (Balmer, 2009, p.558). Furthermore, Fukukawa and colleagues (2007) insist that corporate identity ("what we really are") should be congruent with communication ("what we say we are"). Therefore, when studying the effect of ethical corporate marketing on corporate image, the investigation of corporate communications about ethical subjects should be a priority.

As an aspect of corporate communication, CSR communication "is designed and distributed by the company itself about its CSR efforts" (Morsing, 2006, p.171) and can reflect three potential approaches ( [START_REF] Van De Ven | An ethical framework for the marketing of corporate social responsibility[END_REF]. The reputation management approach focuses "on the basic requirements of conducting a responsible business to obtain and maintain a license to operate from society" (Van de Ven, 2008, p.345) and implies no explicit CSR communication. The second approach, building a virtuous corporate brand, means making an "explicit promise to the stakeholders and the general public that the corporation excels with respect to their CSR endeavours" (Van de Ven, 2008, p.345), which clearly suggests CSR communication. In this sense, two communication instruments are available (Van de Ven, 2008): corporate communication instruments (e.g., CSR reporting, publication of ethical codes, Web sites) and marketing communication instruments (e.g., advertising, sponsoring, direct marketing and promotions, public relations). The latter, which can be overly salient [START_REF] Sjovall | From actions to impressions: cognitive attribution theory and the formation of corporate reputation[END_REF], are riskier and therefore remain less common, despite some recent rapid growth. For example, in France in 2008, 6% of mass media advertisements included messages about company actions to protect the environment, a six-fold increase compared with 2006 [START_REF] Arpp | Advertising and environment 2008[END_REF]. The third, ethical product differentiation approach means "differentiating a certain product or service on the basis of an environmental or social quality" (Van de Ven, 2008, p.348). In this case, CSR efforts constitute the heart of the brand positioning (e.g., The Body Shop, Natura Brasil), which makes CSR communications natural and inevitable.

Managers have long followed a simple principle: Do good and let others talk about it [START_REF] Kotler | Corporate social responsibility. Doing the most good for your company and your cause[END_REF]. Yet the use of CSR communication is growing, in small-and medium-sized enterprises as in multinational corporations [START_REF] Nielsen | CSR communication in small and medium-sized enterprises: a study of the attitudes and beliefs of middle managers[END_REF], in transition markets as in mature economies [START_REF] Grbac | Ethics, social responsibility and business performance in a transition economy[END_REF][START_REF] Alon | Usage of public corporate communications of social responsibility in Brazil, Russia, India and China (BRIC)[END_REF]). The reason is that CSR communication provides a corporate marketing tool that can build a strong corporate image and reputation [START_REF] Balmer | Corporate identity and the advent of corporate marketing[END_REF][START_REF] Balmer | Corporate marketing: apocalypse, advent and epiphany[END_REF][START_REF] Gray | Managing corporate image and corporate reputation[END_REF][START_REF] Hoeffler | Building brand equity through corporate societal marketing[END_REF][START_REF] Balmer | Corporate marketing: integrating corporate identity, corporate branding, corporate communications, corporate image and corporate reputation[END_REF] and achieve social legitimacy [START_REF] Waeraas | Green legitimation: the construction of an environmental ethos[END_REF][START_REF] Vanhamme | Too good to be true! The effectiveness of CSR history in countering negative publicity[END_REF]. However, we know little about how a central group of stakeholders, namely, consumers, actually respond to it.

Controversial effects of CSR communication on consumers

Most empirical studies indicate a strong negative impact of a company's alleged irresponsible acts (e.g., child labour, human rights violations, air and water pollution) on attitudes toward the firm [START_REF] Murray | Using a hierarchy-of-effects approach to gauge the effectiveness of corporate social responsibility to generate goodwill toward the firm: financial versus nonfinancial impacts[END_REF][START_REF] Folkes | Effects of information about firms' ethical and unethical actions on consumers' attitudes[END_REF], as well as on attitudes toward the product and purchase intentions [START_REF] Murray | Using a hierarchy-of-effects approach to gauge the effectiveness of corporate social responsibility to generate goodwill toward the firm: financial versus nonfinancial impacts[END_REF]Swaen andVanhamme, 2004, 2005). [START_REF] Mohr | The effects of corporate social responsibility and price on consumer responses[END_REF] demonstrate the asymmetric impact of societal practices on consumers' perceptions, as suggested by [START_REF] Creyer | The influence of firm behavior on purchase intention: do consumers really care about business ethics?[END_REF]. Strong CSR performance positively influences consumers' attitudes toward the firm and purchase intentions, whereas poor performance damages them even more. Although the negative impact of irresponsible acts is unambiguous, the positive effect of good societal performances is more controversial (Brown and Dacin, 1997;[START_REF] Swaen | See how 'good' we are: the dangers of using corporate social activities in communication campaigns[END_REF][START_REF] Mohr | The effects of corporate social responsibility and price on consumer responses[END_REF]. The main weakness of these research works is that they rarely take into account the "communication" theoretical framework, meaning they do not systematically question the expression of the message, the credibility of the source, or the medium used [START_REF] Du | Maximizing business returns to Corporate Social Responsibility (CSR): the role of CSR communication[END_REF].

To date, the specific effects of proactive CSR communication have received little attention in marketing research. [START_REF] Schlegelmilch | The perils and opportunities of communicating corporate ethics[END_REF] generally discuss the perils and opportunities of communicating corporate ethics. Other works focus on the effect of previous CSR communication in the case of a crisis [START_REF] Swaen | See how 'good' we are: the dangers of using corporate social activities in communication campaigns[END_REF][START_REF] Vanhamme | Too good to be true! The effectiveness of CSR history in countering negative publicity[END_REF]. Benoit-Moreau and Parguel (2010) also demonstrate a positive impact of CSR communication on perceived corporate brand equity, depending on the perceived congruency between the company and the cause supported: The more congruent the engagement, the more efficient is the communication. In the end, Du and colleagues (2010) present a comprehensive conceptual framework of CSR communication.

The investigation of consumers' responses to explicit CSR communication is even more crucial in an actual context, because the profusion of CSR claims has prompted a movement that denounces those advertising agencies that encourage "greenwashing" (Bradford, 2007). Consumers' scepticism toward firms that take opportunistic advantage of sustainable development trends thus is growing [START_REF] Pomering | Advertising corporate social responsibility initiatives to communicate corporate image: Inhibiting scepticism to enhance persuasion[END_REF][START_REF] Du | Maximizing business returns to Corporate Social Responsibility (CSR): the role of CSR communication[END_REF]. If a company focuses badly or too intently on its CSR claims, consumers may believe that it is trying to hide something (Brown and Dacin, 1997). Perceptions of greenwashing or deliberately misleading strategies can damage consumers' attitude toward a company that communicates about its CSR engagements [START_REF] Peattie | Climate change: a social and commercial marketing communications challenge[END_REF], which suggests that the potential benefits of CSR communication for corporate brand evaluation are questionable.

Research needs to determine when and why CSR communication positively enhances corporate brand evaluations and when and why it damages them. Several studies suggest that part of the answer may stem from a greater understanding of how consumers decode the motivations behind CSR communication (Dean, 2004;[START_REF] Pirsch | A framework for understanding corporate social responsibility programs as a continuum: an exploratory study[END_REF][START_REF] Van De Ven | An ethical framework for the marketing of corporate social responsibility[END_REF].

Controllable CSR communication versus uncontrollable CSR information

Two types of CSR information sources differ from a consumer perspective: companycontrolled communication (part of the corporate identity mix, [START_REF] Van Riel | Principles of corporate communication[END_REF] and uncontrolled information, such as word of mouth, mass media, or non-governmental organisations' (NGO) communications [START_REF] Balmer | Corporate identity and corporate communications: creating competitive advantage[END_REF]Balmer et al., 2007;Bernstein, 2009;[START_REF] Du | Maximizing business returns to Corporate Social Responsibility (CSR): the role of CSR communication[END_REF]. With regard to ethical corporate identity, "uncontrolled communication is in need of increased attention" (Balmer et al., 2007, p.9), because consumers have access to independent sources of information and can compare information provided by the company with evaluations from third parties, such as sustainability ratings.

Uncontrolled sources of information have increased in response to consumers' demand for more credible information about environmental concerns. For example, 71% of French consumers report difficulties evaluating the real impact of environmental innovations [START_REF] Ifop | Green label equity[END_REF]. Various third parties, including NGOs, consulting agencies, and media, publish independent general information or sustainability evaluations of companies' CSR practices (e.g., the guide Shopping for a better world, the Web site www.climatecounts.org, the magazine Fortune). [START_REF] Swaen | The use of corporate social responsibility arguments in communication campaigns: does source credibility matter?[END_REF] note that the use of a source that is not perceived as controlled by the company increases the positive impact of CSR campaigns. Information from third parties, such as reviews [START_REF] Chen | Third-party product review and firm marketing strategy[END_REF], ratings [START_REF] Larceneux | Buzz and recommendations on Internet. What impacts on box-office?[END_REF], or visible labels of quality [START_REF] Dickson | Utility of no sweat labels for apparel consumers: profiling label users and predicting their purchases[END_REF], may be influential if they are easily accessible, comprehensible, persuasive, and minimise cognitive requirements for consumers (Carpenter and Larceneux, 2008). Therefore, the interaction between third parties' uncontrolled information and companies' controlled CSR communication may be strategic for determining consumers' attitude toward the corporate brand. We build on attribution theory to derive a clearer understanding of how consumers perceive and respond to CSR communication. Specifically, we investigate the influence of a sustainability rating provided by an uncontrolled information source on consumers' response to the CSR controlled communication issued by a company on its commercial Web site.

CONCEPTUAL FRAMEWORK AND HYPOTHESES

Attribution theory, sustainability ratings, and company's perceived motives

Attribution theory describes the way people make causal inferences to explain their own or others' behaviour [START_REF] Heider | Social perception and phenomenal causality[END_REF][START_REF] Kelley | The processes of causal attribution[END_REF][START_REF] Kelley | Attribution theory and research[END_REF]. In marketing literature, this theory helps explain consumers' responses to product failures [START_REF] Folkes | Consumers reactions to product failure: an attributional approach[END_REF][START_REF] Dawar | Impact of product-harm crisis on brand equity: the moderating role of consumer expectations[END_REF] and their evaluations of companies that engage in social sponsorship [START_REF] Rifon | Congruence effects in sponsorship. The moderating role of sponsor credibility and consumer attributions of sponsor motive[END_REF] or cause-related marketing [START_REF] Ellen | Charitable programs and the retailer: do they mix?[END_REF][START_REF] Dean | Consumer perception of corporate donations. Effects of company reputation for social responsibility and type of donation[END_REF][START_REF] Sjovall | From actions to impressions: cognitive attribution theory and the formation of corporate reputation[END_REF], two forms of CSR engagements. As in previous literature, [START_REF] Heider | Social perception and phenomenal causality[END_REF] framework could be used as a means to explain how consumers interpret the company's CSR communication and react to it. Though Du and colleagues (2010) suggest that favourable CSR attributions are a key challenge of CSR communication, previously, the attribution theory has not been tested experimentally in this specific context.

Following [START_REF] Heider | Social perception and phenomenal causality[END_REF], we distinguish two types of causal attributions for CSR communication: attributions to the dispositions of the actor (intrinsic motives) and attributions to environmental factors (extrinsic motives). When faced with CSR communication, consumers may infer a genuine environmental consciousness by the company (intrinsic motive) or an attempt to take opportunistic advantage of sustainable development trends (extrinsic motive).

When consumers observe that a company communicates about its CSR engagement but have no other information about the firm, they probably attribute this communication to the current sustainability trend, which is an extrinsic motive. In this vein, the more socially desirable the perceived behaviour is, the more extrinsic its causal attribution [START_REF] Kelley | The processes of causal attribution[END_REF].

External information may help the consumer elaborate more informed attributions [START_REF] Kelley | The processes of causal attribution[END_REF]. Sustainability ratings from independent agencies provide this kind of information by summarising stakeholders' evaluations of companies' efforts to take social and environmental principles into account in their activities [START_REF] Gotsi | Corporate reputation: seeking a definition[END_REF]. To predict how consumers may use these ratings to make causal attributions about an advertised engagement, we use [START_REF] Kelley | The processes of causal attribution[END_REF] co-variation model. Three elements constitute this model.

Consensus refers to the degree to which others adopt the same behaviour, distinctiveness to the degree to which this behaviour occurs only within a particular situation or is repeated by the actor in other situations, and consistency to the degree to which the behaviour is repeated across time [START_REF] Sjovall | From actions to impressions: cognitive attribution theory and the formation of corporate reputation[END_REF].

Based on these three elements, the consumer may attribute the company's advertised engagement to extrinsic motives when most of its competitors engage in the same behaviour at the same time (social consensus), when the company engages in only one CSR activity instead of various ones (distinctiveness), or when CSR engagements are not frequent company practices (no consistency). When a company's global sustainability rating, provided by an independent and credible third party, is very positive, it means that the company respects sustainability principles in various ways (i.e., its engagements are non-distinctive) and on a frequent basis (i.e., its engagements are consistent). As a result, consumers should attribute the advertised engagement to the company's genuine social consciousness (i.e., intrinsic motives). In contrast, a poor sustainability rating should drive CSR engagement attributions to more extrinsic motives [START_REF] Regan | Liking and the attribution process[END_REF][START_REF] Sherry | Gift giving in anthropological perspective[END_REF][START_REF] Sjovall | From actions to impressions: cognitive attribution theory and the formation of corporate reputation[END_REF], such as an attempt to take advantage of current trends.

In turn, we suppose that CSR engagement perceived motives should transfer to CSR communication perceived motives according to [START_REF] Feldman | Self-generated validity and other effects of measurement on belief, attitude, intention, and behaviour[END_REF] accessibilitydiagnosticity model. In this model, the likelihood that any chunk of information will be used as an input for judgment depends on the accessibility of this input compared with that of alternative inputs (i.e., perceived vividness) and its diagnosticity (i.e., perceived relevance) [START_REF] Feldman | Self-generated validity and other effects of measurement on belief, attitude, intention, and behaviour[END_REF][START_REF] Herr | Effects of word-of-mouth and product-attribute information on persuasion: an accessibility-diagnosticity perspective[END_REF]. In this research, we consider the attribution about the engagement as the basis on which the attribution regarding the communication forms. As context-based cues, sustainability ratings activate and make salient the attribution regarding the engagement [START_REF] Menon | Behavioral frequency judgments: an accessibility-diagnosticity framework[END_REF], increasing its accessibility. Furthermore, sustainability ratings, which are unambiguous by nature (i.e., without multiple interpretations), should increase the consumer's confidence in the attribution regarding the engagement, which in turn increases the diagnosticity of the latter to form the attribution about the communication [START_REF] Lord | Biased assimilation and attitude polarization: the effects of prior theories on subsequently considered evidence[END_REF]. If consumers have no other information to explain the company's motives to communicate (i.e., are not familiar with the corporate brand and its sustainability activities, as is common), no alternative inputs are accessible, so the transfer from the attribution of the corporate brand's engagement to the attribution of the communication should occur automatically. Therefore, we hypothesise: H1: Consumers perceive a company's motives to communicate as (a) more intrinsic and (b) less extrinsic when the company earns a good rather than a poor sustainability rating.

To gain a deeper understanding of the formation of intrinsic motives, attribution theory also suggests the mediating role of perceived effort.

On the one hand, sustainability ratings may influence the way consumers evaluate the company's general CSR effort after their exposure to the communication. Two identical efforts might be perceived differently by consumers, depending on situational factors [START_REF] Tversky | Judgment under uncertainty: heuristics and biases[END_REF]. In marketing research, many academics support such framing effects and show that when people doubt an offer's credibility, they tend to discount its value compared with offers of an equal amount [START_REF] Gupta | The discounting of discounts and promotion thresholds[END_REF]. In the context of CSR communication, a poor sustainability rating may prompt consumers' scepticism toward the advertised message [START_REF] Du | Maximizing business returns to Corporate Social Responsibility (CSR): the role of CSR communication[END_REF], leading them to discount the company's CSR effort compared with an equivalent CSR engagement communicated without any other information.

On the other hand, attribution theory posits that the amount of effort expended by an actor indicates its intrinsic motives, because such efforts require willingness [START_REF] Weiner | A theory of motive for some classroom experiences[END_REF].

In our study context, a company's perceived effort should reflect the degree of its commitment to the cause, inhibit consumers' scepticism toward the message [START_REF] Pomering | Advertising corporate social responsibility initiatives to communicate corporate image: Inhibiting scepticism to enhance persuasion[END_REF][START_REF] Du | Maximizing business returns to Corporate Social Responsibility (CSR): the role of CSR communication[END_REF] and reveal a genuine social consciousness [START_REF] Ellen | Charitable programs and the retailer: do they mix?[END_REF].

Everything else being equal, the company's motive to engage in good practices should be perceived as more intrinsic when its efforts appear strong rather than weak. In turn, the accessibility-diagnosticity model suggests that the consumer should transfer perceived motives from the advertised engagement to the CSR communication itself. In this sense, we expect that the level of CSR effort, as perceived by consumers on the basis of the company's CSR communication, partially mediates the effect of sustainability ratings on consumers' perceptions of an intrinsic motive. Therefore, we postulate: H2: A company's perceived CSR effort partially mediates the impact of the sustainability rating on its perceived intrinsic motives to communicate.

Perceived motives and corporate brand evaluation

Previous studies investigate the consequences of attributions [START_REF] Kelley | Attribution theory and research[END_REF] and suggest that an attribution of a specific behaviour as intrinsically or extrinsically motivated influences attitudes toward the actor [START_REF] Robertson | Children and commercial persuasion: an attribution theory analysis[END_REF][START_REF] Folkes | Consumers reactions to product failure: an attributional approach[END_REF][START_REF] Klein | Corporate social responsibility and consumers attributions and brand evaluations in a product-harm crisis[END_REF]).

In the context of moral behaviour, the perception of an actor's intrinsic motive reflects the degree to which a person genuinely experiences feelings and suggests recognition of a certain amount of transparency, which increases perceived sincerity [START_REF] Weiner | A cognitive-developmental analysis of achievement and moral judgments[END_REF].

In contrast, a behaviour attributed to extrinsic motives is perceived as dishonest and misleading for the consumer. It suggests that the action would not have been initiated without a reward and therefore appears opportunistic [START_REF] Condry | Enemies of exploration: self-initiated versus other-initiated learning[END_REF][START_REF] Lepper | The hidden costs of reward[END_REF]. In the context of CSR communication, an internal attribution should induce more perceived sincerity, because the communication appears to represent an objective unto itself [START_REF] Ellen | Charitable programs and the retailer: do they mix?[END_REF].

An external attribution instead should induce a perception of self-serving motives (Bendapudi et al., 1996) and therefore weak sincerity.

Finally, previous works reveal the influence of perceived sincerity on message efficiency in the general case of advertising [START_REF] Mackenzie | An empirical examination of the structural antecedents of attitude toward the ad in an advertising pretesting context[END_REF][START_REF] Goldsmith | The impact of corporate credibility and celebrity credibility on consumer reaction to advertisements and brands[END_REF] and the specific context of sponsorship (Barone et al., 2000;[START_REF] Speed | Determinants of sports sponsorship response[END_REF]. These studies focus on the effects of perceived sincerity at the product brand level. For CSR communication, we consider the corporate brand level and adopt the corporate branding paradigm proposed by Balmer and colleagues [START_REF] Balmer | Corporate identity and the advent of corporate marketing[END_REF][START_REF] Balmer | Corporate marketing: integrating corporate identity, corporate branding, corporate communications, corporate image and corporate reputation[END_REF][START_REF] Mukherjee | New frontiers and perspectives in corporate brand management: in search of a theory[END_REF]. We postulate the influence of perceived motives on corporate brand evaluation as follows:

H3: (a) Perceived intrinsic motives increase corporate brand evaluation, whereas (b) perceived extrinsic motives decrease it.

Figure 1 represents the three hypotheses of our conceptual framework.

Insert Figure 1

Sustainability ratings and corporate brand evaluation

To proceed beyond investigating the attribution route that underlies CSR communication mechanisms, we also examine the effect of sustainability ratings on corporate brand building by CSR communication.

Previous research [START_REF] Creyer | The influence of firm behavior on purchase intention: do consumers really care about business ethics?[END_REF][START_REF] Mohr | The effects of corporate social responsibility and price on consumer responses[END_REF] notes the asymmetric effects of societal information on consumers' evaluations, such that negative information (e.g., crises) causes more damage than does positive information provide benefits.

As we mentioned previously, sustainability ratings can induce framing effects and have a priming effect [START_REF] Herr | Priming price: prior knowledge and context effects[END_REF] on subsequent judgments of CSR communication and therefore on corporate brand evaluation. The situation we investigate probably induces an assimilationcontrast effect [START_REF] Sherif | Social judgment: assimilation and contrast effects in communication and attitude change[END_REF], such that judgments of stimuli depend on the context or internal frame within which they are evaluated, not just the intrinsic stimuli characteristics. Thus, an assessment of a stimulus depends on the perceived discrepancy between the stimulus and the frame. If the discrepancy is weak, an assimilation effect occurs, and the judgment's distortion will be weak. If the discrepancy is stronger, a contrast effect will cause the final judgment to be more polarised than in the assimilation case or in a control group without priming.

In application to our study scenario, consumers exposed to a good sustainability rating before their exposure to CSR communication should experience assimilation, so their judgment differences, compared with a group unexposed to external information, should be tenuous. However, consumers exposed to a poor rating before they review the CSR communication should experience a contrast effect that degrades their evaluations even further. Therefore, we postulate: H4: In case of CSR communication, there is an asymmetric effect of sustainability ratings on corporate brand evaluation: A good rating improves it less (vs. no rating) than does a poor rating damage it (vs. no rating).

METHODOLOGY

Experiment and stimuli

To test the hypotheses, we include three different conditions in a between-subjects experimental design (no rating vs. a poor vs. a good sustainability rating by an independent consumers' association) in the context of CSR communication provided by the company.

Brand and sector.

In all conditions, we first present D'ECO, a fictitious retailer in the furniture and home improvement industry, by showing the respondents a corporate Web site home page (see Appendix 1). We choose a fictitious corporate brand, as have many previous studies (Brown and Dacin, 1997;[START_REF] Swaen | The use of corporate social responsibility arguments in communication campaigns: does source credibility matter?[END_REF], to avoid any effects of prior brand familiarity (we checked the availability of the brand name and verified respondents were unfamiliar with it: m = 1.43 on a seven-point scale). Furthermore, for the choice of the product category, we rejected several industries because of their high societal involvement (e.g., sports products, toys), for which ceiling effects might occur, and others that are intrinsically controversial (e.g., alcohol, tobacco), which might boost consumers' suspicion.

In contrast, the furniture and home improvement industry is an experience-driven category, which makes corporate brand evaluation more critical [START_REF] Erdem | Brand equity as a signaling phenomenon[END_REF]. Furthermore, in this sector, many corporate brands (e.g., IKEA) employ a simple brand architecture, in which their corporate brand is the same as their commercial and outlet brands. This characteristic helps remove ambiguity about corporate brand evaluation inferred by consumers. To increase task involvement, the experiment indicates that the fictitious company is a real retailer considering a launch in France.

CSR communication: Web site. We test the brand's commercial Web site (specifically, brand presentation Web page) for four main reasons. First, a Web site is the most frequent medium used to engage in CSR corporate communication [START_REF] Van De Ven | An ethical framework for the marketing of corporate social responsibility[END_REF]Biloslavo and Trnavcevic, 2009); 80% of Fortune 500 companies mention their involvement on their Web sites (Bhattacharya and Sen, 2004;[START_REF] Kim | What they can do versus how much they care: Assessing corporate communication strategies on Fortune 500 web sites[END_REF]. Such societal communication generally requires a highly accessible but inexpensive medium to avoid accusations of spending more on communication than on the initiatives themselves (Varadarajan and Menon, 1998;[START_REF] Schlegelmilch | The perils and opportunities of communicating corporate ethics[END_REF]. Second, Web sites are a preferred medium to communicate CSR involvement because of the richness of argumentation and opportunities for interactivity they provide [START_REF] Coupland | Corporate social responsibility as argument on the web[END_REF]Biloslavo and Trnavcevic, 2009). Third, for product categories such as furniture and home improvement, Web sites are widespread; 47% of French consumers look for information on the Internet before buying furniture in an outlet (Netratings French Panel, 2006). Fourth, brand Web sites can target the best brand clients and influence their attitudes and perceptions of the brand's personality [START_REF] Müller | The impact of a World Wide Web site visit on brand image in the motor vehicle and mobile telephone industries[END_REF]. We therefore anticipate that online CSR communication influences corporate brand evaluation after a single exposure, because corporate image generally is malleable compared with corporate reputation and can be modified rapidly through adequate communication [START_REF] Gray | Managing corporate image and corporate reputation[END_REF].

The brand presentation Web page stimulus features four elements: timeline, facts & figures, our vision, and our engagements. In the generic corporate communication condition, general press information replaces the fourth block, "our engagements" (see Appendix 1).

To ensure realism, we use IKEA's engagements (i.e., producing furniture with wood from certified forests) as inspiration for the environmental claims. We focus on the environmental CSR domain because it represents a universal aspect with high international convergence (i.e., several norms already exist, such as the European Ecolabel, ISO14001, or FSC label to support forest preservation). Furthermore, among societal claims, environmental ones dominate as ecology has achieved tremendous media coverage and is now the most typical domain of CSR [START_REF] Peattie | Climate change: a social and commercial marketing communications challenge[END_REF].

CSR information: Sustainability ratings. The manipulated factor appears in an article extracted from a daily newspaper, Le Monde (equivalent to The New York Times in the United States or The Times in the United Kingdom). The article describes a successful Canadian non-profit organisation that evaluates firms according to various criteria with regard to their sustainable endeavours (see Appendix 1). At the end of the article, it provides the ratings of four companies. In the positive condition (good sustainability rating), D'ECO has always obtained a rating above 8 on a ten-point scale, which puts it among the most virtuous companies in its sector. In the negative condition (poor sustainability rating), D'ECO has always obtained a rating below 2 and falls among the worst companies in its sector. These extreme ratings allow the manipulated information to be diagnostic [START_REF] Herr | Effects of word-of-mouth and product-attribute information on persuasion: an accessibility-diagnosticity perspective[END_REF]. We control for the information's credibility in each condition. In the control condition, the article does not appear at all.

Procedure

The data collection relied on a Web survey, and the experiment consisted of three stages. First, the home page introduced the D'ECO Company and the product categories it sells. Second, the newspaper article containing the ratings appeared. Third, respondents read the Web page stimulus. For each of the three pages (see Appendix 1), a zoom tool enables the respondents to read the material easily, and a "next page" button appears. Then, they completed the questionnaire with no possibility of going back to review the Web pages. Only respondents who noticed that D'ECO supported a cause remain in the final data sample.

To access a generalisable sample, we recruited 122 respondents from the online panel of a professional market research institute. Respondents are between 25 and 45 years of age (mean = 34). The sample represents various areas in France and is heterogeneous in terms of gender and socio-economic status. We randomly assigned the subjects to the three treatments.

Measures and pre-tests

All constructs use seven-point scales. To assess consumers' social consciousness and perceptions of the company's motives and CSR effort, we develop ad-hoc scales. For the other measures, we rely on previously validated scales. Similar to previous research, we assess corporate brand evaluation with a global measure of perceived corporate brand equity (adapted from [START_REF] Yoo | Developing and validating a multidimensional consumerbased brand equity scale[END_REF]. We conduct checks for uni-dimensionality and reliability for the multi-items scales and find satisfactory reliability (see Appendix 2). We use mean item scores to measure the constructs; in Table 1, we provide the scales' means and standard deviations for each of the experimental treatments.

Insert Table 1

RESULTS

To determine the respondents' perceptions of the sustainability ratings, we measure D'ECO's perceived reputation in the case of the poor and good sustainability ratings. The manipulation check confirms that the corporate brand's societal reputation is significantly higher in the good sustainability ratings (m = 5.5) than in the poor sustainability ratings (m = 3.5, t(175) = 9.2, p < .000) condition. Furthermore, the perceived credibility of the newspaper that mentions its sustainability rating is 5.8 on a seven-point scale and does not significantly differ across treatments. Additional analyses show that the three samples are homogenous in terms of their environmental consciousness (χ²(2) = 3.0, ns).

To test H1, we conducted tests of the equality of means, which reveal that sustainability rankings have a significant influence on intrinsic motives but not extrinsic motives. Specifically, respondents perceive the retailer's communication motives as more internal (m = 5.6 vs. 4.2, p < .000) and less external (means of 5.7 vs. 5.7, ns) when the retailer earns a good rather than a poor sustainability rating. Therefore, we find support for H1a but not for H1b.

To test the mediating effect of the retailer's perceived CSR effort on the relationship between the sustainability rating and the retailer's intrinsic motives to communicate, we use three successive regression models, as suggested by [START_REF] Chumpitaz-Caceres | Les processus modérateurs et médiateurs: distinction conceptuelle, aspects analytiques et illustrations[END_REF], and we present the results in Table 2.

Insert Table 2

Model A shows that the company's sustainability rating significantly influences the perceived CSR effort, as it appears in the CSR communication. Model B demonstrates that perceived CSR effort has a significant effect on the retailer's intrinsic motives, even when we control for the sustainability rating (Model C). Thus, the retailer's perceived CSR effort has a partial mediating effect on the impact of sustainability ratings on the retailer's perceived intrinsic motives, in support of H2.

To test H3, we apply a new linear regression model (Model D) that considers the effect of the company's intrinsic and extrinsic motives to communicate on corporate brand evaluation. This model is significant, and as we expected and in support of H3a, the results exhibit the significant and positive effect of consumers' perceptions of intrinsic motives on corporate brand evaluation. However, corporate brand evaluation is not influenced by the company's perceived extrinsic motives, so we must reject H3b.

To further investigate H1, H2 and H3 and check for potential problems of collinearity within constructs measures, we use structural equation modelling. Thus we test the path from sustainability ratings to corporate brand evaluation, going through company's perceived effort and motives (intrinsic and extrinsic). The analysis is indicative as the number of observations is weak (122) for the model complexity (30 parameters), leading to underestimated indicators.

The indicators of model fit are satisfactory, apart from a weak GFI (χ²(48) = 99.4, p = .000, χ²/df = 2.1, goodness-of-fit index = .880, confirmatory fit index = .948, normed fit index = .906, root mean squared error of approximation = .094, square root mean residual = .075).

The four constructs-perceived effort, perceived intrinsic motives, perceived extrinsic motives, and corporate brand evaluation-achieve good levels of reliability (Jöreskog's ρ = .887, .873, .800, and .944, respectively) and convergent validity (average variance extracted = . 797, .697, .572, and .850, respectively). The path coefficients are significant; between the rating and company's perceived effort, the standardised coefficient is .52 (p < .000); between the company's perceived effort and intrinsic motives, the standardised coefficient is .810 (p < .000), and between intrinsic motives and corporate brand evaluation, it is .670 (p < .000).

However they are not significant between perceived effort and extrinsic motives (.030, ns) or between extrinsic motives and corporate brand evaluation (-.046, ns), meaning that brand evaluation is not influenced by perceived effort (and then extrinsic motives). Thus, structural equation modelling tends to confirm the preceding results pertaining to H1, H2 and H3.

Finally, we test our last hypothesis with a one-way ANOVA, which we use to consider the influence of sustainability ratings on corporate brand evaluation when the company uses CSR communications. The ratings have an impact on corporate brand evaluation (F(2,121) = 20.0, p < .000), such that it increases in response to a good sustainability rating (m = 5.5) compared with the control case of no rating (m = 5.0, t(85) = 2.1, p = .035). Similarly, the corporate brand evaluation is lower when the sustainability rating is poor (m = 3.8) compared with the control case (m = 5.0, t(78) = 4.0, p < .000). Sustainability rating knowledge thus appears to leverage the corporate brand evaluation when the rating is good, but it reduces it even more when the rating is poor, in support of H4. Figure 2 depicts this asymmetric effect of sustainability ratings on corporate brand evaluations.

Insert Figure 2

DISCUSSION

Theoretical, managerial, and societal implications

Building on previous works (Balmer andGreyser, 2003, 2007;Balmer et al., 2007;[START_REF] Fukukawa | Mapping the interface between corporate identity, ethics and corporate responsibility[END_REF], this research contributes to a greater understanding of the manner in which consumers, those often forgotten stakeholders, respond to CSR policies in the context of an accessible, consumer goods, corporate brand. We offer several interesting findings regarding how consumers perceive companies' societal communication; in general, we demonstrate the influence of sustainability ratings on perceptions of a company's CSR efforts, which influence their perceptions of the company's motives. As the central variable for evaluations of corporate communications, intrinsic motives have positive effects on corporate brand evaluation. [START_REF] Klein | Corporate social responsibility and consumers attributions and brand evaluations in a product-harm crisis[END_REF] have offered evidence of the central role of perceived motives in their research about client complaints, and [START_REF] Sjovall | From actions to impressions: cognitive attribution theory and the formation of corporate reputation[END_REF] similarly postulate its effect in the specific case of CSR communication, though no work has tested it empirically before now. This empirical confirmation of the relevance of the attribution process for explaining consumers' CSR communication evaluations represents an important result: "Real" consumers examine communication messages and wonder about the company's motives. In a sense, this study replicates previous research pertaining to other communication domains that appear similar to CSR communication, such as sponsorship [START_REF] Rifon | Congruence effects in sponsorship. The moderating role of sponsor credibility and consumer attributions of sponsor motive[END_REF] and causerelated marketing (Dean, 2004). As Rifon and colleagues (2004) provide in their analysis of the impact of sponsor and brand congruence on consumers' responses, we validate the mediating role of a company's intrinsic motives on the effect of CSR communication on corporate brand evaluation.

We also confirm the distinction between extrinsic versus intrinsic company motives.

Motives do not represent opposite sides of the same construct, which actually ranges from altruistic (intrinsic) to opportunistic (extrinsic) motives, but rather form two different dimensions (Pearson ρ = -.046, ns). We thus shed additional light on the different roles these two dimensions play for CSR communication's persuasiveness, in that the only dimension that affects corporate brand evaluation is perceived intrinsic motives. To enhance their corporate brand evaluations, consumers must perceive intrinsic motives for CSR communication. Yet consumers clearly (mean 5.7 out of 7) and homogeneously (std. dev. = 1.0 versus 1.3 for internal motivations) perceive extrinsic motives by companies, though these motives appear well-accepted by French consumers, who understand the economic motives that often underlie sustainable development efforts. They do not necessarily reduce corporate brand evaluation-a positive finding from a managerial point of view.

Beyond generalising the application of attribution theory to a new domain, we investigate a new antecedent of the attribution process, namely, sustainability ratings. The experiment reveals their dual effects on intrinsic motives. Specifically, ratings have a direct effect on perceptions of intrinsic motives, because they act as a signal of the nondistinctiveness and consistency of the engagement communicated with the company's other behaviours. Moreover, this effect is partially mediated by the company's perceived CSR effort, which indicates a framing effect of sustainability ratings that may bias perceptions of the company's CSR efforts. Perceived CSR effort also seems to offer a key variable for explaining CSR communication efficiency; despite its appearance in a few investigations [START_REF] Ellen | Charitable programs and the retailer: do they mix?[END_REF], it clearly deserves more attention to delineate all the factors that influence its evaluation. Sustainability ratings influence intrinsic motives, which is an interesting result in the context of company communications. Companies that display intrinsic motivations earn greater rewards for their efforts, in that their communication more efficiently enhances their corporate brand evaluation. Highlighting their CSR efforts using objective arguments therefore provides a good method for them.

In addition to the findings regarding the attribution process, we offer a fruitful examination of the direct effects of the combination of sustainability ratings and CSR communication on corporate brand evaluation. This study confirms Balmer and colleagues' (2007) intuition that external sources (i.e., uncontrolled information) play important roles in ethical corporate communication. By validating the asymmetric impact of good and poor ratings, we demonstrate that in the case of CSR communication, a good rating has limited impact on corporate brand evaluations relative to the absence of information, whereas a poor rating really damages corporate brand evaluation. On the one hand, we might lament that virtuous companies do not benefit more from their past behaviours compared with "neutral" firms, likely because consumers establish a general climate of confidence in companies, as long as they have not been tainted by scandals or crisis. However, it might be interesting to examine this finding among a population of highly sceptical consumers, because the initial finding reveals only an average opinion. Moreover, we might theorise that consumers' confidence decreases as more denunciations identify abuses and as they learn more about ecological issues. On the other hand, corporate brand evaluation declines with poor ratings, which appear to inform perceptions of CSR communication. Therefore, in response to the profusion of CSR claims, independent information about companies' sustainability performance helps consumers explicate CSR communication more accurately.

From a broader societal perspective, sustainability ratings play a significant role in helping consumers make more responsible evaluations, which may have great value, especially when consumers appear weakly sceptical. Such sources of information can penalise non-virtuous companies through classical market mechanisms, sensitise consumers further, and encourage virtuous firms to persevere in their CSR practices. Sustainability ratings thus can resolve the prisoner's dilemma evoked in the introduction. Yet a question still arises: Should governments ensure the availability and seriousness of such sources? The task would not be easy, considering the complexity of analysing the global environment impact of every company's activities, but a potential approach could compel firms to publish a certified report, similar to requirements in the accounting domain.

Limitations and directions for further research

Despite its contributions, this research is not without limitations. First, we rely on fictitious, and therefore less realistic, stimuli. Although a fictitious company enables us to focus on the effects of societal information rather than any pre-existing knowledge respondents might possess about a real company, further research should investigate more realistic stimuli.

Second, it would be interesting to replicate our results in other cultural contexts, because CSR consciousness may vary across them [START_REF] Grbac | Ethics, social responsibility and business performance in a transition economy[END_REF]. Third, the furniture and home improvement product category generally displays an intermediate level of CSR communication intensity (cf. grocery retailers) and an intermediate level of perceived risk regarding CSR issues (cf. oil companies). We suspect the attribution process may be less significant in sectors in which CSR communication is a prerequisite, because consumers probably treat the information more superficially, but more significant in controversial sectors, which boost consumers' suspicions. Fourth, sustainability ratings affect corporate brand evaluations when consumers have not developed any comprehensive frame to explain the company's CSR communication. When consumers benefit from pre-existing, specific knowledge (e.g., about the company's or sector-specific practices) that explains CSR communication motives, the automatic influence from the advertised engagement to the CSR communication, as we postulated in H1 and H2, might be moderated. Fifth, our experiment only manipulates support for an environmental cause (i.e., forest preservation). Extending the research to other causes, other forms of involvement (e.g., waste and energy reduction, product life cycle optimisation), or other media (e.g., traditional advertising, packaging) would be interesting directions for further research.

In addition to these experimental replications, investigating signals other than sustainability ratings and their effects on a company's perceived intrinsic motives could deepen our understanding of attribution processes. If the diffusion of sustainability ratings is not within the company's control, perhaps more controllable signals, such as the nature and amount of involvement, the communication medium, the message, or the means of communicating, offer areas for further study. that considers the societal implications, as well as the managerial implications, of marketing activities, supporting Lazer's (1969, p.3) early intuition that "Marketing is not an end in itself. It is not the exclusive province of business management. Marketing must serve not only business but also the goals of society. It must act in concert with broad public interest. For marketing does not end with the buy-sell transaction-its responsibilities extend well beyond making profits." Barone, M.J., Miyazaki, A.D. and Taylor, K.A.: 2000, "The influence of cause-related marketing on consumer choice: does one good turn deserve another?", Journal of the Academy of Marketing Science, 28(2), 248-262. Bendapudi, N., Singh, S. and Bendapudi, V.: 1996, "

  Enhancing helping behavior: an integrative framework for promotion planning", Journal of Marketing, 60(3), 33-49. Benoit-Moreau, F. and Parguel, B.: 2010, "Building brand equity with environmental communication: an empirical investigation in France", Euromed Journal of Business (forthcoming). Bernstein, D.: 2009, "Rhetoric and reputation: some thoughts on corporate dissonance", Management Decision, 47(4) 603-615. Bhattacharya, C.B. and Sen, S.: 2004, "Doing better at doing good: when, why and how consumers respond to corporate social initiatives", California Management Review, 47(1), 9-24. Biloslavo, R. and Trnavcevic, A.: 2009, "Web sites as tools of communication of a "green" company", Management Decision, 47(7), 1158-1173. Bradford, R.: 2007, "Greenwash confronted: misleading advertisement regulation in .org/corporates/pdf/greenwash_confronted.pdf. Brown, T.J. and Dacin, P.A.: 1997, "The company and the product: corporate associations and consumer product responses", Journal of Marketing, 61(1), 68-84. Carpenter, M. and Larceneux, F.: 2008, "Label equity and the effectiveness of values-based labels: an experiment with two French PGI labels", International Journal of Consumer Studies, 32(5), 499-519.

FigureFigure 2 :

 2 Figure 1: Conceptual framework

Table 1 : Descriptive statistics per treatment

 1

			CSR perceived effort	Intrinsic motives	Extrinsic motives	Corporate brand evaluation
	Good rating	Mean	5.7	5.6	5.7	5.5
	(N=42)	Std dev.	1.0	0.8	1.0	1.0
	No rating	Mean	5.7	5.4	5.6	5.0
	(N=45)	Std dev.	1.2	1.2	1.1	1.4
	Poor rating	Mean	4.6	4.2	5.7	3.8
	(N=35)	Std dev.	1.3	1.4	0.9	1.1

Table 2 : Regression results

 2

	Model	Dependent Variable (Y)	Independent Variables (X i )	Adj R²	Sd β β β β	T
		Perceived effort		0.095
	A		(intercept)			14.7
			Rating		0.321***	3.7
		Intrinsic motives		0.506
	B		(intercept)			3.4
			Perceived effort		0.714***	11.2
		Intrinsic motives		0.533
	C		(intercept) Rating		0.185**	2.6 2.8
			Perceived effort		0.654***	9.9
		Corporate brand evaluation		0.313
			(intercept)			3.1
	D		Intrinsic motives		0.565***	7.5
			Extrinsic motives		-0.053	-0.7

***p < .001, **p < .01, *p < .05.