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This paper reports on the genome analysis of strain F29 representing a new species of the genus Thermosulfurimonas . This strain, isolated from the Lucky Strike hydrothermal vent field on the Mid-Atlantic Ridge, is able to grow by disproportionation of S0 with CO2 as a carbon source. Strain F29 possesses a genome of 2,345,565 bp, with a G+C content of 58.09%, and at least one plasmid. The genome analysis revealed complete sets of genes for CO2 fixation via the Wood–Ljungdahl pathway, for sulphate-reduction and for hydrogen oxidation, suggesting the involvement of the strain into carbon, sulphur, and hydrogen cycles of deep-sea hydrothermal vents. Strain F29 genome encodes also several CRISPR sequences, suggesting that the strain may be subjected to viral attacks. Comparative genomics was carried out to decipher sulphur disproportionation pathways. Genomes of sulphur-disproportionating bacteria from marine hydrothermal vents were compared to the genomes of non-sulphur-disproportionating bacteria. This analysis revealed the ubiquitous presence in these genomes of a molybdopterin protein consisting of a large and a small subunit, and an associated chaperone. We hypothesize that these proteins may be involved in the process of elemental sulphur disproportionation.

Hyperthermophilic archaea of the genus Archaeoglobus are the subject of many fundamental and biotechnological researches. Despite their significance, the class Archaeoglobi is currently represented by only eight species obtained as axenic cultures and taxonomically characterized. Here, we report the isolation and characterization of a new species of Archaeoglobus from a deep-sea hydrothermal vent (Mid-Atlantic Ridge, TAG) for which the name Archaeoglobus neptunius sp. nov. is proposed. The type strain is SE56T (=DSM 110954T = VKM B-3474T). The cells of the novel isolate are motile irregular cocci growing at 50–85°C, pH 5.5–7.5, and NaCl concentrations of 1.5–4.5% (w/v). Strain SE56T grows lithoautotrophically with H2 as an electron donor, sulfite or thiosulfate as an electron acceptor, and CO2/HCO3− as a carbon source. It is also capable of chemoorganotrophic growth by reduction of sulfate, sulfite, or thiosulfate. The genome of the new isolate consists of a 2,115,826 bp chromosome with an overall G + C content of 46.0 mol%. The whole-genome annotation confirms the key metabolic features of the novel isolate demonstrated experimentally. Genome contains a complete set of genes involved in CO2 fixation via reductive acetyl-CoA pathway, gluconeogenesis, hydrogen and fatty acids oxidation, sulfate reduction, and flagellar motility. The phylogenomic reconstruction based on 122 conserved single-copy archaeal proteins supported by average nucleotide identity (ANI), average amino acid identity (AAI), and alignment fraction (AF) values, indicates a polyphyletic origin of the species currently included into the genus Archaeoglobus, warranting its reclassification.

A novel extreme thermophilic and piezophilic chemoorganoheterotrophic archaeon, strain EXT12cT, was isolated from a hydrothermal chimney sample collected at a depth of 2496 m at the East Pacific Rise 9° N. Cells were strictly anaerobic, motile cocci. The strain grew at NaCl concentrations ranging from 1 to 5 % (w/v; optimum, 2.0%), from pH 6.0 to 7.5 (optimum, pH 6.5–7.0), at temperatures between 60 and 95 °C (optimum, 80–85 °C), and at pressures from 0.1 to at least 50 MPa (optimum, 30 MPa). Strain EXT12cT grew chemoorganoheterotrophically on complex proteinaceous substrates. Its growth was highly stimulated by the presence of elemental sulphur or l-cystine, which were reduced to hydrogen sulfide. The DNA G+C content was 54.58 mol%. Phylogenetic analyses based on 16S rRNA gene sequences and concatenated ribosomal protein sequences showed that strain EXT12cT falls into the genus Thermococcus and is most closely related to Thermococcus nautili strain 30-1T. Overall genome relatedness index analyses (average nucleotide identity scores and in silico DNA–DNA hybridizations) showed a sufficient genomic distance between the new genome and the ones of the Thermococcus type strains for the delineation of a new species. On the basis of genotypic and phenotypic data, strain EXT12cT is considered to represent a novel species, for which the name Thermococcus henrietii sp. nov. is proposed, with the type strain EXT12cT (=UBOCC M-2417T=DSM 111004T).

International audience; A novel anaerobic methylotrophic halophilic methanogen strain SLHTYRO T was isolated from a deep hypersaline anoxic basin called "Tyro" located in the Eastern Mediterranean Sea. Cells of SLHTYRO T were motile cocci. The strain SLHTYRO T grew between 12 and 37 °C (optimum 30 °C), at pH between 6.5 and 8.2 (optimum pH 7.5) and salinity from 45 to 240 g L −1 NaCl (optimum 135 g L −1). Strain SLHTYRO T was methylotrophic methanogen able to use methylated compounds (trimethylamine, dimethylamine, monomethylamine and methanol). Strain SLHTYRO T was able to grow at in situ hydrostatic pressure and temperature conditions (35 MPa, 14 °C). Phylogenetic analysis based on 16S rRNA gene and mcrA gene sequences indicated that strain SLHTYRO T was affiliated to genus Methanohalophilus within the order Methanosarcinales. It shared >99.16% of the 16S rRNA gene sequence similarity with strains of other Methanohalophilus species. Based on ANIb, AAI and dDDH measurements, and the physiological properties of the novel isolate, we propose that strain SLHTYRO T should be classified as a representative of a novel species, for which the name Methanohalophilus profundi sp. nov. is proposed; the type strain is SLHTYRO T (=DSM 108854 = JCM 32768 = UBOCC-M-3308).

International audience; Thermosulfurimonas marina strain SU872 T is a thermophilic, anaerobic, chemolithoautotrophic bacterium, isolated from a shallow-sea hydrothermal vent in the Pacific Ocean near Kunashir Island, that is able to grow by disproportionation of inorganic sulfur compounds and dissimilatory nitrate reduction to ammonium. Here we report the complete genome sequence of strain SU872 T , which presents one circular chromosome of 1,763,258 bp with a mean G + C content of 58.9 mol%. The complete genome harbors 1827 predicted protein-encoding genes, 47 tRNA genes and 3 rRNA genes. Genes involved in sulfur and nitrogen metabolism were identified. This study expands our knowledge of sulfur and nitrogen use in energy metabolism of high temperatures areas of shallow-sea hydrothermal environments. In order to highlight Thermosulfurimonas marina metabolic features, its genome was compared with that of Thermosulfurimonas dismutans, the only other species described within the Thermosulfurimonas genus.

International audience; Thermosulfuriphilus ammonigenes ST65 T is an anaerobic thermophilic bacterium isolated from a deep-sea hy-drothermal vent chimney. T. ammonigenes is an obligate chemolithoautotroph utilizing elemental sulfur as an electron donor and nitrate as an electron acceptor with sulfate and ammonium formation. It also is able to grow by disproportionation of elemental sulfur, thiosulfate and sulfite. Here, we present the complete genome sequence of strain ST65 T. The genome consists of a single chromosome of 2,287,345 base pairs in size and has a G + C content of 51.9 mol%. The genome encodes 2172 proteins, 48 tRNA genes, and 3 rRNA genes. Genome analysis revealed a complete set of genes essential to CO 2 fixation and gluconeogenesis. Homologs of genes encoding known enzyme systems for nitrate ammonification are absent in the genome of T. ammonigenes assuming unique mechanism for this pathway. The genome of strain ST65 T encodes a complete set of genes necessary for dissimilatory sulfate reduction, which are probably involved in sulfur disproportionation and anaerobic oxidation. This is the first reported genome of a bacterium from the genus Thermosulfuriphilus, providing insights into the microbial contribution into carbon, sulfur and nitrogen cycles in the deep-sea hydro-thermal vent environment.

Thermosulfurimonas marina strain SU872

Thermosulfuriphilus ammonigenes ST65

We are indebted to L. Correia of the Paris Sud Ouest PAPPSO proteomics core facility (http://papso.inra.fr) which is supported by INRA (http://www.inra.fr), the Ile-de-France regional council (https://www.iledefrance.fr/education-recherche), IBiSA (https://www.ibisa.net) and CNRS (http://www.cnrs.fr) for LC/MS analyses and to L. Correia. We thank Y. Quentin for its expertise in taxonomic identification of archaeal Csl4 and Rrp41 members, L.Plassart and J. Caumes for technical help and P. Vitali and M. Kwapisz for helpful discussions.; International audience; A network of RNA helicases, endoribonucleases and exoribonucleases regulates the quantity and quality of cellular RNAs. To date, mechanistic studies focussed on bacterial and eukaryal systems due to the challenge of identifying the main drivers of RNA decay and processing in Archaea. Here, our data support that aRNase J, a 5'-3' exoribonuclease of the β-CASP family conserved in Euryarchaeota, engages specifically with a Ski2-like helicase and the RNA exosome to potentially exert control over RNA surveillance, at the vicinity of the ribosome. Proteomic landscapes and direct protein-protein interaction analyses, strengthened by comprehensive phylogenomic studies demonstrated that aRNase J interplay with ASH-Ski2 and a cap exosome subunit. Finally, Thermococcus barophilus whole-cell extract fractionation experiments provide evidences that an aRNase J/ASH-Ski2 complex might exist in vivo and hint at an association of aRNase J with the ribosome that is emphasised in absence of ASH-Ski2. Whilst aRNase J homologues are found among bacteria, the RNA exosome and the Ski2-like RNA helicase have eukaryotic homologues, underlining the mosaic aspect of archaeal RNA machines. Altogether, these results suggest a fundamental role of β-CASP RNase/helicase complex in archaeal RNA metabolism.

The icy satellites of Jupiter and Saturn are perhaps the most promising places in the Solar System regarding habitability. However, the potential habitable environments are hidden underneath km-thick ice shells. The discovery of Enceladus’ plume by the Cassini mission has provided vital clues in our understanding of the processes occurring within the interior of exooceans. To interpret these data and to help configure instruments for future missions, controlled laboratory experiments and simulations are needed. This review aims to bring together studies and experimental designs from various scientific fields currently investigating the icy moons, including planetary sciences, chemistry, (micro-)biology, geology, glaciology, etc. This chapter provides an overview of successful in situ, in silico, and in vitro experiments, which explore different regions of interest on icy moons, i.e. a potential plume, surface, icy shell, water and brines, hydrothermal vents, and the rocky core.

Viruses represent a driving force in the evolution of microorganisms including those thriving in extreme environments. However, our knowledge of the viral diversity associated to microorganisms inhabiting the deep-sea hydrothermal vents remains limited. The phylum of Thermotogae, including thermophilic bacteria, is well represented in this environment. Only one virus was described in this phylum, MPV1 carried by Marinitoga piezophila. In this study, we report on the functional and genomic characterization of two new bacterioviruses that infect bacteria from the Marinitoga genus. Marinitoga camini virus 1 and 2 (MCV1 and MCV2) are temperate siphoviruses with a linear dsDNA genome of 53.4 kb and 50.5 kb respectively. Here, we present a comparative genomic analysis of the MCV1 and MCV2 viral genomes with that of MPV1. The results indicate that even if the host strains come from geographically distant sites, their genomes share numerous similarities. Interestingly, heavy metals did not induce viral production, instead the host of MCV1 produced membrane vesicles. This study highlights interaction of mobile genetic elements (MGE) with their hosts and the importance of including hosts-MGEs' relationships in ecological studies.

Information on the biochemical pathways of carbon and energy metabolism in representatives of the deep lineage bacterial phylum Deferribacteres are scarce. Here, we report the results of the sequencing and analysis of the high-quality draft genome of the thermophilic chemolithoautotrophic anaerobe Deferribacter autotrophicus. Genomic data suggest that CO2 assimilation is carried out by recently proposed reversible tricarboxylic acid cycle (&ldquo, roTCA cycle&rdquo, ). The predicted genomic ability of D. autotrophicus to grow due to the oxidation of carbon monoxide was experimentally proven. CO oxidation was coupled with the reduction of nitrate to ammonium. Utilization of CO most likely involves anaerobic [Ni, Fe]-containing CO dehydrogenase. This is the first evidence of CO oxidation in the phylum Deferribacteres. The genome of D. autotrophicus encodes a Nap-type complex of nitrate reduction. However, the conversion of produced nitrite to ammonium proceeds via a non-canonical pathway with the participation of hydroxylamine oxidoreductase (Hao) and hydroxylamine reductase. The genome contains 17 genes of putative multiheme c-type cytochromes and &ldquo, e-pilin&rdquo, genes, some of which are probably involved in Fe(III) reduction. Genomic analysis indicates that the roTCA cycle of CO2 fixation and putative Hao-enabled ammonification may occur in several members of the phylum Deferribacteres.

International audience; Methanofervidicoccus sp. A16 is a novel thermophilic and obligate hydrogenotrophic methanogen isolated from a deep-sea hydrothermal vent chimney sample at the Mid Cayman spreading center, Caribbean Sea. Here we report the complete genome of strain A16, which has one circular chromosome of 1,485,358 bp with a mean G+C content of 35.01 mol%. The complete genome harbors 1442 predicted protein-encoding genes. Genes involved in hydrogenotrophic methane production and N 2 fixation were identified in this genome. This study expands our knowledge of methanogenesis at high temperatures and the involvement of these microorganisms in the carbon and nitrogen cycles of deep-sea hydrothermal environments.

Microorganisms can increase the open-circuit potential of stainless steel immersed in seawater of several hundred millivolts in a phenomenon called ennoblement. It raises the chance of corrosion as the open-circuit potential may go over the pitting corrosion potential. Despite the large impact of the ennoblement, no unifying mechanisms have been described as responsible for the phenomenon. Here we show that the strict electrotroph bacterium "Candidatus Tenderia electrophaga" is detected as an ennoblement biomarker and is only present at temperatures at which we observe ennoblement. This bacterium was previously enriched in biocathode systems. Our results suggest that "Candidatus Tenderia electrophaga," and its previously described extracellular electron transfer metabolism coupled to oxygen reduction activity, could play a central role in modulating stainless steel open-circuit potential and consequently mediating ennoblement.

International audience; In live cells, high concentrations up to 300-400 mg/mL, as in Eschericia coli (Ellis, R J. Curr. Opin. Struct. Biol. 2001, 11, 114) are achieved which have effects on their proper functioning. However, in many experiments only individual parts of the cells as proteins or membranes are studied in order to get insight into these specific components and to avoid the high complexity of whole cells, neglecting by the way the influence of crowding. In the present study, we investigated cells of the order of Thermococcales, which are known to live under extreme conditions, in their intact form and after cell lysis to extract the effect of crowding on the molecular dynamics of the proteome and of water molecules. We found that some parameters characterizing the dynamics within the cells seem to be intrinsic to the cell type, as flexibility typical for the proteome, others are more specific to the cellular environment, as bulk water's residence time and some fractions of particles participating to the different motions, which make the lysed cells' dynamics similar to the one of another Thermococcale adapted to live under high hydrostatic pressure. In contrast to studies on the impact of crowding on pure proteins we show here that the release of crowding constraints on proteins leads to an increase in the rigidity and a decrease in the high pressure sensitivity. In a way similar to high pressure adaptation in piezophiles, the hydration water layer is decreased for the lysed cells, demonstrating a first link between protein adaptation and the impact of crowding or osmolytes on proteins.

Transcriptomes were analyzed for two related hyperthermophilic archaeal species, the piezophilic Thermococcus barophilus strain MP and piezosensitive Thermococcus kodakarensis strain KOD1 subjected to high hydrostatic pressures. A total of 378 genes were differentially expressed in T. barophilus cells grown at 0.1, 40 and 70 MPa, whereas 141 genes were differentially regulated in T. kodakarensis cells grown at 0.1 and 25 MPa. In T. barophilus cells grown under stress conditions (0.1 and 70 MPa), 178 upregulated genes were distributed among three clusters of orthologous groups (COG): energy production and conversion (C), inorganic ion transport and metabolism (P) and carbohydrate transport and metabolism (G), whereas 156 downregulated genes were distributed among: amino acid transport and metabolism (E), replication, recombination and repair (L) and nucleotide transport and metabolism (F). The expression of 141 genes was regulated in T. kodakarensis cells grown under stress conditions (25 MPa); 71 downregulated genes belong to three COG: energy production and conversion (C), amino acid transport and metabolism (E) and transcription (K), whereas 70 upregulated genes are associated with replication, recombination and repair (L), coenzyme transport (H) and defense mechanisms (V).

International audience; Prokaryotes inhabiting in the deep sea vent ecosystem will thus experience harsh conditions of temperature, pH, salinity or high hydrostatic pressure (HHP) stress. Among the fifty-two piezophilic and piezotolerant prokaryotes isolated so far from different deep-sea environments, only fifteen (four Bacteria and eleven Archaea) that are true hyper/thermophiles and piezophiles have been isolated from deep-sea hydrothermal vents; these belong mainly to the Thermococcales order. Different strategies are used by microorganisms to thrive in deep-sea hydrothermal vents in which "extreme" physico-chemical conditions prevail and where non-adapted organisms cannot live, or even survive. HHP is known to impact the structure of several cellular components and functions, such as membrane fluidity, protein activity and structure. Physically the impact of pressure resembles a lowering of temperature, since it reinforces the structure of certain molecules, such as membrane lipids, and an increase in temperature, since it will also destabilize other structures, such as proteins. However, universal molecular signatures of HHP adaptation are not yet known and are still to be deciphered.

A thermophilic, anaerobic, iron-reducing bacterium (strain DY22619T) was isolated from a sulfide sample collected from an East Pacific Ocean hydrothermal field at a depth of 2901 m. Cells were Gram-stain-negative, motile rods (2–10 µm in length, 0.5 µm in width) with multiple peritrichous flagella. The strain grew at 40–70 °C inclusive (optimum 60 °C), at pH 4.5–8.5 inclusive (optimum pH 7.0) and with sea salts concentrations of 1–10 % (w/v) (optimum 3 % sea salts) and NaCl concentrations of 1.5–5.0 % (w/v) (optimum 2.5 % NaCl). Under optimal growth conditions, the generation time was around 55 min. The isolate was an obligate chemoorganoheterotroph, utilizing complex organic compounds, amino acids, carbohydrates and organic acids including peptone, tryptone, beef extract, yeast extract, alanine, glutamate, methionine, threonine, fructose, mannose, galactose, glucose, palatinose, rhamnose, turanose, gentiobiose, xylose, sorbose, pyruvate, tartaric acid, α-ketobutyric acid, α-ketovaleric acid, galacturonic acid and glucosaminic acid. Strain DY22619T was strictly anaerobic and facultatively dependent on various forms of Fe(III) as an electron acceptor: insoluble forms and soluble forms. It did not reduce sulfite, sulfate, thiosulfate or nitrate. The genomic DNA G+C content was 29.0 mol%. Phylogenetic 16S rRNA gene sequence analyses revealed that the closest relative of strain DY22619T was Caloranaerobacter azorensis MV1087T, sharing 97.41 % 16S rRNA gene sequence similarity. On the basis of physiological distinctness and phylogenetic distance, the isolate is considered to represent a novel species of the genus Caloranaerobacter , for which the name Caloranaerobacter http://dx.doi.org/10.1601/nm.4081 ferrireducens sp. nov. is proposed. The type strain is DY22619T ( = JCM 19467T = DSM 27799T = MCCC1A06455T).

Prokaryotic viruses play a major role in the microbial ecology and evolution. However, the virosphere associated with deep-sea hydrothermal ecosystems remains largely unexplored. Numerous instances of lateral gene transfer have contributed to the complex and incongruent evolutionary history of Thermotogales, an order well represented in deep-sea hydrothermal vents. The presence of clustered regularly interspaced short palindromic repeats (CRISPR) loci has been reported in all Thermotogales genomes, suggesting that these bacteria have been exposed to viral infections that could have mediated gene exchange. In this study, we isolated and characterized the first virus infecting bacteria from the order Thermotogales, Marinitoga piezophila virus 1 (MPV1). The host, Marinitoga piezophila is a thermophilic, anaerobic and piezophilic bacterium isolated from a deep-sea hydrothermal chimney. MPV1 is a temperate Siphoviridae-like virus with a 43.7 kb genome. Surprisingly, we found that MPV1 virions carry not only the viral DNA but preferentially package a plasmid of 13.3 kb (pMP1) also carried by M. piezophila. This ‘menage a trois’ highlights potential relevance of selfish genetic elements in facilitating lateral gene transfer in the deep-sea biosphere.

Phaeobacter leonis strain 306T is an alphaproteobacterium isolated from Mediterranean Sea sediments. It belongs to the genus Phaeobacter, which was recently proposed and is still poorly characterized. In an effort to better understand the fundamental aspects of the microbiology of this genus, we present here the 4.82-Mb draft genome sequence of Phaeobacter leonis strain 306T.

Phaeobacter leonis strain 306 T is an alphaproteobacterium isolated from Mediterranean Sea sediments. It belongs to the genus Phaeobacter , which was recently proposed and is still poorly characterized. In an effort to better understand the fundamental aspects of the microbiology of this genus, we present here the 4.82-Mb draft genome sequence of Phaeobacter leonis strain 306 T .

Members of the genus Halomonas are physiologically versatile and harbor ecological adaptations enabling the colonization of contrasted environments. We present here the draft genome of Halomonas lionensis RHS90 T , isolated from Mediterranean Sea sediments. Numerous genes related to stress tolerance, DNA repair, or external signal-sensing systems were predicted, which could represent selective advantages of this marine bacterium.

The complete genome sequence of Methanohalophilus halophilus DSM 3094 T , a member of the Methanosarcinaceae family and the Methanosarcianales order, consists of 2,022,959 bp in one contig and contains 2,137 predicted genes. The genome is consistent with a halophilic methylotrophic anaerobic lifestyle, including the methylotrophic and CO 2 -H 2 methanogensis pathways.

A novel sulfur-reducing bacterium, strain K6013(T), was isolated from a sulfide sample collected at a depth of 2771 m from a high-temperature hydrothermal vent in the Indian Ocean. Cells were Gram-stain-negative, anaerobic, motile rods (0.92.2 x 0.4-0.6 mu m). The strain grew at NaCl concentrations ranging from 1 to 4.5% (w/v) (optimum 2.5 %), at pH 5 to 8 (optimum pH 6), and at temperatures between 40 and 75 degrees C (optimum 65 degrees C). K6013(T) was an obligate chemolithoautotroph, using thiosulfate, sulfur and nitrate as terminal electron acceptors in the presence of H-2 but not sulfate, sulfite nor nitrite. The major cellular fatty acids were C-16 : 0 (17.4 %), C-18 : 1 omega 7c/C-18 : 1 omega 6c (ummed feature 8, 37.91 %), C-18 : 0 (18.29 %) and C-14 : 0 3-OH/iso-C-16: I-1 (summed feature 2, 8.56 %). The DNA G+C content was 38.2 mol%. The results of phylogenetic 16S rRNA gene sequence analyses indicated that K6013(T) represents a member of the genus Desulfurobacterium within the class Aquificae, with highest sequence similarity of 96.93% to Desulfurobacterium atlanticum SL22(T). On the basis of genotypic and phenotypic data, K6013(T) is considered to represent a novel species of the genus Desulfurobacterium, for which the name Desulfurobacterium indicum sp. nov. is proposed, with the type strain K6013(T) (=DSM 101677(T)=MCCC 1A01868(T)).

Members of the order Thermococcales are common inhabitants of high-temperature hydrothermal vent systems (black smokers) that are represented in clone libraries mostly by isolates from the Thermococcus genus. We report the complete sequence of a novel species from the Pyrococcus genus, P. kukulkanii strain NCB100, which has been isolated from a flange fragment of the Rebecca’s Roost hydrothermal vent system in the Guaymas Basin.

Kosmotoga pacifica strain SLHLJ1T is a thermophilic chemoorganoheterotrophic bacterium isolated from a deep-sea hydrothermal sediment. It belongs to the physiologically homogeneous Thermotogaceae family. Here, we describe the phenotypic features of K. pacifica together with its genome sequence and annotation. The chromosome has 2,169,170 bp, organized in one contig. A total of 1897 candidate protein-encoding genes and 177 RNA genes were identified. The 16S rRNA gene sequence of this strain is distantly related to sequences of some relatives classified in the same genus (K. olearia 7.02% and K. shengliensis 7.83%), with dissimilarity percentages close to the threshold generally described for genus delineation. Nevertheless, the percentage of conserved proteins (POCP), which is much higher than 50% (around 70%), together with phenotypic features of the isolates, confirm the affiliation all Kosmotoga species described so far to the same genus. Electronic supplementary material The online version of this article (doi:10.1186/s40793-016-0214-2) contains supplementary material, which is available to authorized users.

Dimethylsulfoniopropionate (DMSP) is an abundant osmolyte and anti-stress compound produced primarily in marine ecosystems. After its release into the environment, microorganisms can exploit DMSP as a source of sulfur and carbon, or accumulate it as an osmoprotectant. However, import systems for this ecophysiologically important compatible solute, and its stress-protective properties for microorganisms that do not produce it are insufficiently understood. Here we address these questions using a well-characterized set of Bacillus subtilis mutants to chemically profile the influence of DMSP import on stress resistance, the osmostress-adaptive proline pool and on osmotically controlled gene expression. We included in this study the naturally occurring selenium analogue of DMSP, dimethylseleniopropionate (DMSeP), as well as a set of synthetic DMSP derivatives. We found that DMSP is not a nutrient for B. subtilis, but it serves as an excellent stress protectant against challenges conferred by sustained high salinity or lasting extremes in both low and high growth temperatures. DMSeP and synthetic DMSP derivatives retain part of these stress protective attributes, but DMSP is clearly the more effective stress protectant. We identified the promiscuous and widely distributed ABC transporter OpuC as a high-affinity uptake system not only for DMSP, but also for its natural and synthetic derivatives.

European Community project MAMBA (FP7-KBBE-2008-226977). This grant BIO2011-25012 from the Spanish Ministry of Economy and Competitiveness (formerly MICINN). European Commission for ‘MicroB3’ grant (FP7-OCEAN.2011-2 (contract Nr 287589)). Government of Canada through Genome Canada and the Ontario Genomics Institute (grant 2009-OGI-ABC-1405) and U.S. National Institutes of Health (grants GM074942 and GM094585). Midwest Center for Structural Genomics).

A novel halophilic bacterium, strain RHS90 T , was isolated from marine sediments from the Gulf of Lions, in the Mediterranean Sea. Its metabolic and physiological characteristics were examined under various cultural conditions, including exposure to stressful ones (oligotrophy, high pressure and high concentrations of metals). Based on phylogenetic analysis of the 16S rRNA gene, the strain was found to belong to the genus Halomonas in the class Gammaproteobacteria. Its closest relatives are Halomonas axialensis and Halomonas meridiana (98% similarity). DNAeDNA hybridizations indicated that the novel isolate is genotypically distinct from these species. The DNA G þ C content of the strain is 54.4 mol%. The main fatty acids (C18:1 u7c, 2-OH iso-C15:0 ,C 16:0 and/or C19:0 cyclo u8c), main polar lipids (diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unidentified phosphoglycolipid) and major respiratory quinone (ubiquinone Q9) were determined. The novel isolate is heterotrophic, mesophilic, euryhaline (growth optimum ranging from 2 to 8% w/v NaCl) and is able to grow under stressful conditions. The strain accumulates poly-b-hydroxyalkanoates granules and compatible solutes. Based on genotypic, chemotaxonomic and phenotypic distinctiveness, this isolate is likely to represent a novel species, for which the name Halomonas lionensis is proposed. The type strain of H. lionensis is RHS90 T (DSM 25632 T ¼ CIP 110370 T ¼ UBOCC 3186 T ). © 2014 Published by Elsevier Masson SAS on behalf of Institut Pasteur.

The majority of the biosphere is a high pressure environment. Around 70% of the marine biosphere lies at depths below 1000 m, i.e. at pressures of 100 bars or higher. To survive in these environments, deep-biosphere organisms have adapted to life at high pressure. In vitro studies showed that the activity of certain proteins originating from deep-sea organisms is less affected by high pressure than that of enzymes from surface organisms . However, the genetic and structural bases for this increased pressure resistance are still unknown. Elastic incoherent neutron scattering studies, which provide access to information about molecular dynamics, constitute a very promising approach to decipher the structural adaptation in proteins living under high pressure. This approach has been used in the past to investigate the adaptation of biological systems to temperature and salinity and proved to be essential and complementary to structural studies. Here first investigations of high pressure effects on cell dynamics are presented using Thermococcales as models.

The gill chamber of deep-sea hydrothermal vent shrimp Rimicaris exoculata hosts a dense community of epibiotic bacteria dominated by filamentous Epsilonproteobacteria and Gammaproteobacteria. Using metagenomics on shrimp from the Rainbow hydrothermal vent field, we showed that both epibiont groups have the potential to grow autotrophically and oxidize reduced sulfur compounds or hydrogen with oxygen or nitrate. For carbon fixation, the Epsilonproteobacteria use the reductive tricarboxylic acid cycle, whereas the Gammaproteobacteria use the Calvin–Benson–Bassham cycle. Only the epsilonproteobacterial epibionts had the genes necessary for producing ammonium. This ability likely minimizes direct competition between epibionts and also broadens the spectrum of environmental conditions that the shrimp may successfully inhabit. We identified genes likely to be involved in shrimp–epibiont interactions, as well as genes for nutritional and detoxification processes that might benefit the host. Shrimp epibionts at Rainbow are often coated with iron oxyhydroxides, whose origin is intensely debated. We identified 16S rRNA sequences and functional genes affiliated with iron-oxidizing Zetaproteobacteria, which indicates that biological iron oxidation might play a role in forming these deposits. Fluorescence in situ hybridizations confirmed the presence of active Zetaproteobacteria in the R. exoculata gill chamber, thus providing the first evidence for a Zetaproteobacteria–invertebrate association.

A hyperthermophilic, anaerobic, piezophilic archaeon (strain DY20341T) was isolated from a sediment sample collected from an East Pacific Ocean hydrothermal field (1° 37′ S 102° 45′ W) at a depth of 2737 m. The cells were irregular cocci, 0.8–1.5 µm in diameter. Growth was observed between 50 and 90 °C (optimum 80 °C), pH 5.0 and 8.0 (optimum pH 7.0), 1 % and 7 % (w/v) sea salts (Sigma, optimum 3 %), 1 % and 4 % (w/v) NaCl (optimum 3 %) and 0.1 and 80 MPa (optimum 30 MPa). The minimum doubling time was 66 min at 30 MPa and 80 °C. The isolate was an obligate chemoorganoheterotroph, capable of utilizing complex organic compounds and organic acids including yeast extract, peptone, tryptone, casein, starch, Casamino acids, citrate, lactate, acetate, fumarate, propanoate and pyruvate for growth. It was strictly anaerobic and facultatively dependent on elemental sulfur or sulfate as electron acceptors, but did not reduce sulfite, thiosulfate, Fe(III) or nitrate. The presence of elemental sulfur enhanced growth. The G+C content of the genomic DNA was 43.6±1 mol%. 16S rRNA gene sequence analysis revealed that the closest relative of the isolated organism was Palaeococcus ferrophilus DMJT (95.7 % 16S rRNA gene similarity). On the basis of its physiological properties and phylogenetic analyses, the isolate is considered to represent a novel species, for which the name Palaeococcus pacificus sp. nov. is proposed. The type strain is strain DY20341T ( = JCM 17873T = DSM 24777T).

Nicotinamidases catalyze the hydrolysis of the amide bond in nicotinamide to produce ammonia and nicotinic acid. These enzymes are an essential component of the NAD+ salvage pathway and are implicated in the viability of several pathogenic organisms. Its absence in humans makes them a promising drug target. In addition, although they are key analytical biocatalysts for screening modulators in relevant biomedical enzymes, such as sirtuins and poly-ADP-ribosyltransferases, no commercial sources are available. Surprisingly, the finding of an affordable source of nicotinamidase from metagenomic libraries is hindered by the absence of a suitable and fast screening method. In this manuscript, we describe the development of two new whole-cell methods using the chemical property of one of the products formed in the enzymatic reaction (pyrazinoic or nicotinic acid) to form colored complexes with stable iron salts, such as ammonium ferrous sulfate or sodium nitroprusside. After optimization of the assay conditions, a fosmid polygenomic expression library obtained from deep-sea mesophilic bacteria was screened, discovering several positive clones with the ammonium ferrous sulfate method. Their quantitative rescreening with the sodium nitroprusside method allowed the finding of the first nicotinamidase with balanced catalytic efficiency towards nicotinamide (nicotinamidase activity) and pyrazinamide (pyrazinamidase activity). Its biochemical characterization has also made possible the development of the first high-throughput whole-cell method for prescreening of new nicotinamidase inhibitors by the naked eye, saving time and costs in the design of future antimicrobial and antiparasitic agents.

A novel sulfate-reducing bacterium, strain J2(T), was isolated from a serpentinized peridotite sample from the Indian Ocean. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J2(T) clustered with the genus Desulfovibrio within the family Desulfovibrionaceae, but it showed low similarity (87.95 %) to the type species Desulfovibrio desulfuricans DSM 642(T). It was most closely related to Desulfovibrio portus MSL79(T) (96.96 %), followed by Desulfovibrio aespoeensis Aspo-2(T) (96.11 %), Desulfovibrio piezophilus C1TLV30(T) (96.04 %) and Desulfovibrio profundus DSM 11384(T) (95.17 %). Other available sequences shared less than 93.33 % 16S rRNA gene sequence similarity. Cells were Gram-staining-negative, anaerobic, motile vibrios (2-6 x 0.4-0.6 mu m). Growth was observed at salinities ranging from 0.2 to 6 % (optimum 2.5 %), from pH 5 to 8 (optimum pH 6.5-7) and at temperatures between 9 and 40 degrees C (optimum 30-35 degrees C). J2(T) was piezophilic, growing optimally at 10 MPa (range 0-30 MPa). J2(T) used lactate, malate, pyruvate, formate and hydrogen as energy sources. Sulfate, thiosulfate, sulfite, fumarate and nitrate were used as terminal electron acceptors. Lactate and pyruvate were fermented. The main fatty acids were iso-C-15:0, anteiso-C-15:0, summed feature 9 (iso-C-17:1 omega 9c and/or C-16:0 10-methyl) and iso-C-17:0. The DNA G+C content of strain J2(T) was 63.5 mol%. The combined genotypic and phenotypic data show that strain J2(T) represents a novel species of a novel genus in the family Desulfovibrionaceae, for which the name Pseudodesulfovibrio indicus gen. nov., sp. nov. is proposed, with the type strain J2(T) (= MCCC 1A01867(T) = DSM 101483(T)). We also propose the reclassification of D. piezophilus as Pseudodesulfovibrio piezophilus comb. nov., D. profundus as Pseudodesulfovibrio profundus comb. nov., D. portus as Pseudodesulfovibrio portus comb. nov. and D. aespoeensis as Pseudodesulfovibrio aespoeensis comb. nov.

A novel sulfate-reducing bacterium, strain S606(T), was isolated from a sulfide sample collected at a depth of 2764 m from a deep-sea vent chimney wall in the Indian Ocean. Phylogenetic 16S rRNA gene sequence analyses placed strain S606(T) within the genus Thermodesulfatator, with highest sequence similarity of 98.2% to Thermodesulfatator indicus DSM 15286(T), followed by Thermodesulfatator atlanticus AT1325(T) (97.4 %). The average nucleotide identity (ANI) values between S606(T) and the two other type strains (T. indicus DSM 15286(T) and T. atlanticus AT1325(T)) were 79.2% and 71.5 %, respectively. The digital DNA-DNA hybridization estimate values between S606(T) and these two type strains were 22.7 +/- 2.4% and 18.1 +/- 2.3 %, respectively. Cells were Gram-stain-negative, anaerobic, motile rods (1-1.8 +/- 0.5-0.7 mu m). The novel isolate grew at NaCl concentrations ranging from 1.5 to 4.5% (optimum 2.5-3 %), from pH 5.5 to 8 (optimum 6.5-7.0) and at temperatures between 50 and 80 degrees C (optimum 65-70 degrees C). S606(T) grew chemolithoautotrophically in an H-2/CO2 atmosphere (80 : 20, v/v; 200 kPa), used sulfate as a terminal electron acceptor, but not sulfur, sulfite nor thiosulfate. The predominant fatty acids were C-16 : 0(24.2 %), summed feature 8 (C-18 : 1 omega 6c and/or C-18 : 1 omega 7c, 26.3 %), C-18 : 0 (22.2 %) and C-18 : 1 omega 9c (9.2 %). The DNA G + C content of the chromosomal DNA was 43.1 mol%. The combined genotypic, chemotaxonomic and phenotypic traits show that S606(T) should be described as representing a novel species of the genus Thermodesulfatator, for which the name Thermodesulfatator autotrophicus sp. nov. is proposed. The type strain is S606(T) (= DSM 101864(T) = MCCC 1A01871(T)).

Water and protein dynamics on a nanometer scale were measured by quasi-elastic neutron scattering in the piezophile archaeon Thermococcus barophilus and the closely related pressure-sensitive Thermococcus kodakarensis, at 0.1 and 40 MPa. We show that cells of the pressure sensitive organism exhibit higher intrinsic stability. Both the hydration water dynamics and the fast protein and lipid dynamics are reduced under pressure. In contrast, the proteome of T. barophilus is more pressure sensitive than that of T. kodakarensis. The diffusion coefficient of hydration water is reduced, while the fast protein and lipid dynamics are slightly enhanced with increasing pressure. These findings show that the coupling between hydration water and cellular constituents might not be simply a master-slave relationship. We propose that the high flexibility of the T. barophilus proteome associated with reduced hydration water may be the keys to the molecular adaptation of the cells to high hydrostatic pressure.

Pyrococcus yayanosii CH1, as the first and only obligate piezophilic hyperthermophilic microorganism discovered to date, extends the physical and chemical limits of life on Earth. It was isolated from the Ashadze hydrothermal vent at 4,100 m depth. Multi-omics analyses were performed to study the mechanisms used by the cell to cope with high hydrostatic pressure variations. In silico analyses showed that the P. yayanosii genome is highly adapted to its harsh environment, with a loss of aromatic amino acid biosynthesis pathways and the high constitutive expression of the energy metabolism compared with other non-obligate piezophilic Pyrococcus species. Differential proteomics and transcriptomics analyses identified key hydrostatic pressure-responsive genes involved in translation, chemotaxis, energy metabolism (hydrogenases and formate metabolism) and Clustered Regularly Interspaced Short Palindromic Repeats sequences associated with Cellular apoptosis susceptibility proteins.

The complete genome sequence of Desulfovibrio indicus J2 T , a member of the family Desulfovibrionaceae , consists of 3,966,573-bp in one contig and encodes 3,461 predicted genes, 5 noncoding RNAs, 3 rRNAs operons, and 52 tRNA-encoding genes. The genome is consistent with a heterotrophic, anaerobic lifestyle including the sulfate reduction pathway.

International audience; A novel hyperthermophilic, piezophilic, anaerobic archaeon, designated NCB100(T), was isolated from a hydrothermal vent flange fragment collected in the Guaymas basin at the hydrothermal vent site named 'Rebecca's Roost' at a depth of 1997 m. Enrichment and isolation were performed at 100 degrees C under atmospheric pressure. Cells of strain NCB100(T) were highly motile, irregular cocci with a diameter of -1 mu m. Growth was recorded at temperatures between 70 and 112 degrees C (optimum 105 degrees C) and hydrostatic pressures of 0.1-80 MPa (optimum 40-50 MPa). Growth was observed at pH 3.5-8.5 (optimum pH 7) and with 1.5-7% NaCl (optimum at 2.5-3 %). Strain NCB100(T) was a strictly anaerobic chemo-organoheterotroph and grew on complex proteinaceous substrates such as yeast extract, peptone and tryptone, as well as on glycogen and starch. Elemental sulfur was required for growth and was reduced to hydrogen sulfide. The fermentation products from complex proteinaceous substrates were CO2 and H-2. The G+C content of the genomic DNA was 41.3 %. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain NCB100(T) belongs to the genus Pyrococcus, showing 99% similarity with the other described species of the genus Pyrococcus. On the basis of physiological characteristics, DNA G+C content, similarity level between ribosomal proteins and an average nucleotide identity value of 79 %, strain NCB100(T) represents a novel species for which the name Pyrococcus kukulkanii sp. nov. is proposed. The type strain is NCB100(T) (=DSM 101590(T) =Souchotheque de Bretagne BG1337(T)).