Marinitoga aeolica sp. nov., a novel thermophilic anaerobic heterotroph isolated from a shallow hydrothermal field of Panarea Island in the Aeolian archipelago, Italy.

A novel thermophilic strain, designated BP5-C20AT, was isolated from the shallow hydrothermal field of the Panarea island in the Aeolian archipelago close to Sicily, Italy. Cells are motile rods surrounded with a 'toga', Gram-stain-negative and display a straight to curved morphology during the exponential phase. Strain BP5-C20AT is thermophilic (optimum 55 °C), moderately acidophilic (optimum pH 5.6) and halotolerant (optimum 25 g l-1 NaCl). It can use yeast extract, peptone and tryptone. It uses the following carbohydrates: cellobiose, fructose, glucose, maltose, starch, sucrose and xylan. Elemental sulphur is used as an electron acceptor and reduced to hydrogen sulphide. The predominant cellular fatty acid is C16 : 0. Phylogenetic analysis showed that strain BP5-C20AT shared 97.3 % 16S rRNA gene sequence identity with the closest related species Marinitoga lauensis LG1T. The complete genome of strain BP5-C20AT is 2.44 Mb in size with a G+C content of 27.3 mol%. The dDDH and ANI values between the genomes of strains BP5-C20AT and M. lauensis LG1T are 31.0 and 85.70% respectively. Finally, from its physiological, metabolic and genomic characteristics, strain BP5-C20AT (=DSM 112332T=JCM 39183 T) is proposed as representative of a novel species of the genus Marinitoga named Marinitoga aeolica sp. nov. and belonging to the order Petrotogales, in the phylum Thermotogota.

Thermospira aquatica gen. nov., sp. nov., a novel thermophilic spirochete isolated from a Tunisian hot spring, and description of the novel family Thermospiraceae.

A novel thermophilic, anaerobic bacterium, strain F1F22T, was isolated from hot spring water collected in northern Tunisia. The cells were non-motile, Gram-negative and helical with hooked ends, 0.5×10-32 µm in size. Growth of the strain was observed at 45-70 °C (optimum, 55 °C), in 0.0-1.0 % (w/v) NaCl (optimum without NaCl) and at pH 6.5-8.5 (optimum, pH 7.5). Yeast extract was required for growth, and the strain grew on glucose, sucrose and maltose. The major fatty acids were C16:0 (40.2 %), iso-C16: 0 (30.2 %) and C16 :0 DMA (14.5 %). The genome consisted of a circular chromosome (2.5 Mb) containing 2672 predicted protein-encoding genes with a G+C content of 43.15 mol %. Based on a comparative 16S rRNA gene sequence analysis, strain F1F22T formed a deeply branching lineage within the phylum Spirochaetota, class Spirochaetia, order Brevinematales, and had only low sequence similarity to other species of the phylum (lower than 83 %). Genome-based analysis of average nucleotide identity and digital DNA-DNA hybridization of strain F1F22T with Treponema caldarium DSM 7334T, Brevinema andersonii ATCC 43811T and Spirochaeta thermophila DSM 6578T showed values between 63.26 and 63.52 %, and between 20 and 25 %. Hence, we propose strain F1F22T as a representative of a novel family (Thermospiraceae fam. nov.), genus and species of Brevinematales: Thermospira aquatica gen. nov., sp. nov. (type strain F1F22T=JCM 31314T=DSM 101182T).

Methanobacterium alkalithermotolerans sp. nov., a novel alkaliphilic and hydrogen-utilizing methanogen isolated from an alkaline geothermal spring (La Crouen, New Caledonia).

An anaerobic, hydrogenotrophic methane-producing archaeon was isolated from an alkaline thermal spring (42 °C, pH 9.0) in New Caledonia. This methanogen, designated strain CANT, is alkaliphilic, thermotolerant, with Gram-positive staining non-motile cells. Strain CANT grows autotrophically using hydrogen exclusively as an energy source and carbon dioxide as the sole carbon source (without the requirement of yeast extract or other organic compounds). It grows at 20-45 °C (optimum, 45 °C) and pH 7.3-9.7 (optimum, pH 9.0). NaCl is not required for growth (optimum 0 %) but is tolerated up to 1.5 %. It resists novobiocin, streptomycin and vancomycin but is inhibited by ampicillin and penicillin, among other antibiotics. The genome consists of a circular chromosome (2.2 Mb) containing 2126 predicted protein-encoding genes with a G+C content of 36.4 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain CANT is a member of the genus Methanobacterium, most closely related to the alkaliphilic Methanobacterium alcaliphilum WeN4T with 98.5 % 16S rRNA gene sequence identity. The genomes of strain CANT and M. alcaliphilum DSM 3459, sequenced in this study, share 71.6 % average nucleotide identity and 14.0 % digital DNA-DNA hybridization. Therefore, phylogenetic and physiological results indicate that strain CANT represents a novel species, for which the name Methanobacterium alkalithermotolerans sp. nov. is proposed, and strain CANT (=DSM 102889T= JCM 31304T) is assigned as the type strain.

Alkalicella caledoniensis gen. nov., sp. nov., a novel alkaliphilic anaerobic bacterium isolated from 'La Crouen' alkaline thermal spring, New Caledonia.

A novel anaerobic, alkaliphilic, mesophilic, Gram-stain-positive, endospore-forming bacterium was isolated from an alkaline thermal spring (42 °C, pH 9.0) in New Caledonia. This bacterium, designated strain LB2T, grew at 25-50 °C (optimum, 37 °C) and pH 8.2-10.8 (optimum, pH 9.5). Added NaCl was not required for growth (optimum, 0-1 %) but was tolerated up to 7 %. Strain LB2T utilized a limited range of substrates, such as peptone, pyruvate, yeast extract and xylose. End products detected from pyruvate fermentation were acetate and formate. Both ferric citrate and thiosulfate were used as electron acceptors. Elemental sulphur, nitrate, nitrite, fumarate, sulphate, sulfite and DMSO were not used as terminal electron acceptors. The two major cellular fatty acids were iso-C15 : 0 and C16 : 0. The genome consists of a circular chromosome (3.7 Mb) containing 3626 predicted protein-encoding genes with a G+C content of 36.2 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that the isolate is a member of the family Proteinivoraceae, order Clostridiales within the phylum Firmicutes. Strain LB2T was most closely related to the thermophilic Anaerobranca gottschalkii LBS3T (93.2 % 16S rRNA gene sequence identity). Genome-based analysis of average nucleotide identity and digital DNA-DNA hybridization of strain LB2T with A. gottschalkii LBS3T showed respective values of 70.8 and 13.4 %. Based on phylogenetic, genomic, chemotaxonomic and physiological properties, strain LB2T is proposed to represent the first species of a novel genus, for which the name Alkalicella caledoniensis gen. nov., sp. nov. is proposed (type strain LB2T=DSM 100588T=JCM 30958T).

Serpentinicella alkaliphila gen. nov., sp. nov., a novel alkaliphilic anaerobic bacterium isolated from the serpentinite-hosted Prony hydrothermal field, New Caledonia.

A novel anaerobic, alkaliphilic, Gram-stain-positive, spore-forming bacterium was isolated from a carbonaceous hydrothermal chimney in Prony Bay, New Caledonia. This bacterium, designated strain 3bT, grew at temperatures from 30 to 43 °C (optimum 37 °C) and at pH between 7.8 and 10.1 (optimum 9.5). Added NaCl was not required for growth (optimum 0-0.2 %, w/v), but was tolerated at up to 4 %. Yeast extract was required for growth. Strain 3bT utilized crotonate, lactate and pyruvate, but not sugars. Crotonate was dismutated to acetate and butyrate. Lactate was disproportionated to acetate and propionate. Pyruvate was degraded to acetate plus trace amounts of hydrogen. Growth on lactate was improved by the addition of fumarate, which was used as an electron acceptor and converted to succinate. Sulfate, thiosulfate, elemental sulfur, sulfite, nitrate, nitrite, FeCl3, Fe(III)-citrate, Fe(III)-EDTA, chromate, arsenate, selenate and DMSO were not used as terminal electron acceptors. The G+C content of the genomic DNA was 33.2 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that the isolate is a member of the family Clostridiaceae, order Clostridiales within the phylum Firmicutes. Strain 3bT was most closely related to 'Alkaliphilus hydrothermalis' FatMR1T (92.2 % 16S rRNA gene sequence similarity), and was positioned approximately equidistantly between the genera Alkaliphilus, Anaerovirgula and Natronincola. On the basis of phylogenetic, genetic, chemotaxonomic and physiological properties, strain 3bT is proposed to represent a novel species of a new genus, for which the name Serpentinicella alkaliphila gen. nov., sp. nov. is proposed. The type strain of Serpentinicella alkaliphila is 3bT (=DSM 100013T=JCM 30645T).

Balneicella halophila gen. nov., sp. nov., an anaerobic bacterium, isolated from a thermal spring and description of Balneicellaceae fam. nov.

A mesophilic anaerobic bacterium, designated KHALHBd91T was isolated from the moderately hot spring of Hammam Biadha, Tunisia. The strain was Gram-staining-negative, non-sporulating, non-motile and rod-shaped, appearing singly (0.5-2.0×0.5-1 µm). It grew anaerobically at temperatures between 20 and 50 °C (optimum 37 °C) and at pH values between 5.5 and 7.8 (optimum 7.0). It required NaCl for growth, with growth observed at up 8.5 % and an optimum at 2.5 %. KHALHBd91T used glucose, galactose, maltose, pyruvate, lactate, fumarate and yeast extract as electron donors. The end-products from glucose fermentation were acetate, propionate, succinate and CO2. Nitrate, nitrite, thiosulfate, elemental sulfur, sulfate and sulfite were not used as terminal electron acceptors. The predominant cellular fatty acids were anteiso-C15 : 0 and iso-C15 : 0. The respiratory quinone was MK-6. The main polar lipids consisted of lipids, phospholipids, glycolipids, aminolipids, phosphoaminoglycolipids and phosphatidylethanolamine. The DNA G+C content was 35.0 mol%. Phylogenetic analysis of the small-subunit ribosomal 16S rRNA gene sequence indicated that KHALHBd91T had Marinifilum fragile and Marinifilum flexuosum (phylum Bacteroidetes, class Bacteroidia, order Bacteroidales) as its closest relatives (similarity of 86.7 and 87.8 % respectively). The phylogenetic and physiological data fro the present study strongly indicate that the isolate represents a novel genus and species of a novel family, Balneicella halophila gen. nov., sp. nov., in the family Balneicellaceaefam. nov. The type strain is KHALHBd91T (=DSM28579T=JCM19909T).

Aminobacterium thunnarium sp. nov., a mesophilic, amino acid-degrading bacterium isolated from an anaerobic sludge digester, pertaining to the phylum Synergistetes.

A new Gram-staining-positive, non-sporulating, mesophilic, amino acid-degrading anaerobic bacterium, designated strain OTA 102(T), was isolated from an anaerobic sequencing batch reactor treating wastewater from cooking tuna. The cells were curved rods (0.6-2.5×0.5 µm) and occurred singly or in pairs. The strain was motile by means of one lateral flagellum. Strain OTA 102(T) grew at temperatures between 30 and 45 °C (optimum 40 °C), between pH 6.0 and 8.4 (optimum pH 7.2) and NaCl concentrations between 1 and 5 % (optimum 2 %, w/v). Strain OTA 102(T) required yeast extract for growth. Serine, threonine, glycine, cysteine, citrate, fumarate, α-ketoglutarate and pyruvate were fermented. When co-cultured with Methanobacterium formicicum as the hydrogen scavenger, strain OTA 102(T) oxidized alanine, valine, leucine, isoleucine, aspartate, tyrosine, methionine, histidine and asparagine. The genomic DNA G+C content of strain OTA 102(T) was 41.7 mol%. The main fatty acid was iso-C15 : 0. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain OTA 102(T) was related to Aminobacterium colombiense and Aminobacterium mobile (95.5 and 95.2 % similarity, respectively), of the phylum Synergistetes. On the basis of phylogenetic, genetic and physiological characteristics, strain OTA 102(T) is proposed to represent a novel species of the genus Aminobacterium, Aminobacterium thunnarium sp. nov. The type strain is OTA 102(T) ( = DSM 27500(T) = JCM 19320(T)).

Fusibacter fontis sp. nov., a sulfur-reducing, anaerobic bacterium isolated from a mesothermic Tunisian spring.

Strain KhalAKB1T, a mesophilic, anaerobic, rod-shaped bacterium, was isolated from water collected from a mesothermic Tunisian spring. Cells were Gram-staining-positive rods, occurring singly or in pairs and motile by one lateral flagellum. Strain KhalAKB1T grew at 15-45 °C (optimum 30 °C), at pH 5.5-8.5 (optimum pH 7.0) and in the presence of 0-35 g NaCl l- 1 (optimum 1 g NaCl l- 1). It fermented yeast extract and a wide range of carbohydrates including cellobiose, d-glucose, d-ribose, sucrose, d-xylose, maltose, d-galactose and starch as electron donors. Acetate, ethanol, CO2 and H2 were end products of glucose metabolism. It reduced elemental sulfur, but not sulfate, thiosulfate or sulfite, into sulfide. The DNA G+C content was 37.6 mol%. The predominant cellular fatty acids were C14 : 0 and C16 : 0. Phylogenetic analysis of the 16S rRNA gene sequence suggested Fusibacter bizertensis as the closest relative of this isolate (identity of 97.2 % to the type strain). Based on phenotypic, phylogenetic and genotypic taxonomic characteristics, strain KhalAKB1T is proposed to be assigned to a novel species within the genus Fusibacter, order Clostridiales, Fusibacter fontis sp. nov. The type strain is KhalAKB1T ( = DSM 28450T = JCM 19912T).

Crassaminicella profunda gen. nov., sp. nov., an anaerobic marine bacterium isolated from deep-sea sediments.

A novel, anaerobic, chemo-organotrophic bacterium, designated strain Ra1766H(T), was isolated from sediments of the Guaymas basin (Gulf of California, Mexico) taken from a depth of 2002  m. Cells were thin, motile, Gram-stain-positive, flexible rods forming terminal endospores. Strain Ra1766H(T) grew at temperatures of 25-45 °C (optimum 30 °C), pH 6.7-8.1 (optimum 7.5) and in a salinity of 5-60 g l(-1) NaCl (optimum 30 g l(-1)). It was an obligate heterotrophic bacterium fermenting carbohydrates (glucose and mannose) and organic acids (pyruvate and succinate). Casamino acids and amino acids (glutamate, aspartate and glycine) were also fermented. The main end products from glucose fermentation were acetate, butyrate, ethanol, H2 and CO2. Sulfate, sulfite, thiosulfate, elemental sulfur, fumarate, nitrate, nitrite and Fe(III) were not used as terminal electron acceptors. The predominant cellular fatty acids were C14  : 0, C16 : 1ω7, C16 : 1ω7 DMA and C16 : 0. The main polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phospholipids. The G+C content of the genomic DNA was 33.7 mol%. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Ra1766H(T) was affiliated to cluster XI of the order Clostridiales, phylum Firmicutes. The closest phylogenetic relative of Ra1766H(T) was Geosporobacter subterraneus (94.2% 16S rRNA gene sequence similarity). On the basis of phylogenetic inference and phenotypic properties, strain Ra1766H(T) ( = DSM 27501(T) = JCM 19377(T)) is proposed to be the type strain of a novel species of a novel genus, named Crassaminicella profunda.

Characterization of Desulfovibrio biadhensis sp. nov., isolated from a thermal spring.

A novel anaerobic, mesophilic, slightly halophilic sulfate-reducing bacterium, designated strain Khaled BD4(T), was isolated from waters of a Tunisian thermal spring. Cells were vibrio-shaped or sigmoids (5-7×1-1.5 µm) and occurred singly or in pairs. Strain Khaled BD4(T) was Gram-stain-negative, motile and non-sporulated. It grew at 25-45 °C (optimum 37 °C), at pH 5.5-8.3 (optimum pH 7.0) and with 0.5-8% NaCl (optimum 3%). It required vitamins or yeast extract for growth. Sulfate, thiosulfate, sulfite and elemental sulfur served as terminal electron acceptors, but not fumarate, nitrate or nitrite. Strain Khaled BD4(T) utilized H2 in the presence of 2 mM acetate (carbon source), but also lactate, formate, pyruvate and fumarate in the presence of sulfate. Lactate was incompletely oxidized to acetate. Amongst substrates used, only pyruvate was fermented. Desulfoviridin and c-type cytochrome were present. The G+C content of the DNA was 54.6 mol%. The main fatty acids were anteiso -C(15 : 0), iso-C(18 : 0), iso-C(17 : 0) and iso-C(14 : 0). Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Khaled BD4(T) had Desulfovibrio giganteus DSM 4123(T) (96.7% similarity) as its closest phylogenetic relative. On the basis of 16S rRNA gene sequence comparisons together with genetic and physiological characteristics, strain Khaled BD4(T) is assigned to a novel bacterial species, for which the name Desulfovibrio biadhensis sp. nov. is proposed. The type strain is Khaled BD4(T) ( = DSM 28904(T) = JCM 30146(T)).

Acetoanaerobium pronyense sp. nov., an anaerobic alkaliphilic bacterium isolated from a carbonate chimney of the Prony Hydrothermal Field (New Caledonia).

A novel anaerobic bacterial strain, ST07-YET, was isolated from a carbonate chimney of the Prony Hydrothermal Field (PHF) in New Caledonia. Cells were Gram-stain-positive, straight rods (0.7-0.8 × 3.0-5.0 µm) and motile by means of lateral flagella. Strain ST07-YET was mesophilic (optimum 35 °C), moderately alkaliphilic and halotolerant (optimum pH 8.7 and 5 g l- 1 NaCl). Elemental sulfur, sulfate, thiosulfate, sulfite, nitrate and nitrite were not used as terminal electron acceptors. Yeast extract, peptone, tryptone, Casamino acids, crotonate, pyruvate, galactose, maltose, sucrose, ribose, trehalose and glucose were used as carbon sources. Glucose fermentation led to acetate, H2 and CO2 formation. Arginine, serine, histidine, lysine, methionine and cysteine improved growth, but the Stickland reaction was negative for the combinations of amino acids tested. The major metabolic products from yeast extract fermentation were H2, CO2, acetate, butyrate, isobutyrate, isovalerate and propionate. The predominant cellular fatty acids were C16 : 0, C16 : 1cis9, C14 : 0 and C16 : 1cis7 (>5 % of total fatty acids). The G+C content of the genomic DNA was 32.9 mol%. Phylogenetic analysis revealed that strain ST07-YET was most closely related to Clostridium sticklandii DSM 519T and Acetoanaerobium noterae NOT-3T (96.7 % and 96.8 % 16S rRNA gene sequence similarity, respectively). On the basis of phylogenetic, chemotaxonomic and physiological properties, strain ST07-YET is proposed to represent a novel species of the genus Acetoanaerobium (order Clostridiales, phylum Firmicutes) with the name Acetoanaerobium pronyense sp. nov. The type strain is ST07-YET ( = DSM 27512T = JCM 19400T).

Characterization of Alkaliphilus hydrothermalis sp. nov., a novel alkaliphilic anaerobic bacterium, isolated from a carbonaceous chimney of the Prony hydrothermal field, New Caledonia.

A novel anaerobic, alkaliphilic, Gram-positive staining bacterium was isolated from a hydrothermal chimney in the Prony Bay, New Caledonia. This strain designated FatMR1(T) grew at temperatures from 20 to 55 °C (optimum 37 °C) and at pH between 7.5 and 10.5 (optimum 8.8-9). NaCl is not required for growth (optimum 0.2-0.5%), but is tolerated up to 3%. Sulfate, thiosulfate, elemental sulfur, sulfite, nitrate and nitrite are not used as terminal electron acceptors. Strain FatMR1(T) fermented pyruvate, yeast extract, peptone and biotrypcase and used fructose as the only sugar. The main fermentation products from fructose and proteinaceous compounds (e.g. peptone and biotrypcase) were acetate, H2 and CO2. Crotonate was disproportionated to acetate and butyrate. The predominant cellular fatty acids were C14:0 and C16:0. The G + C content of the genomic DNA was 37.1 mol%. On the basis of phylogenetic, genetic, and physiological properties, strain FatMR1(T) (=DSM 25890(T), =JCM 18390(T)) belonging to the phylum Firmicutes, class Clostridia, order Clostridiales, is proposed as a novel species of the genus Alkaliphilus, A. hydrothermalis sp. nov.

Diversity of magnetotactic bacteria from a French pristine Mediterranean area.

Magnetotactic bacteria synthesize intracellular magnetite and/or greigite magnetosome crystals. They play a significant role in both iron and sulfur cycles in sedimentary aquatic environments. To get insight into the bio-geochemical contribution of MTB, more studies concerning their ecology and their distribution in diverse habitats are necessary. The MTB community of an oil-industry polluted area of the French Mediterranean coast has been previously investigated. Here, we investigate the MTB community from coastal sediments of a Mediterranean pristine area using optical and transmission electron microscopy and phylogenetic analysis based on 16S rRNA gene sequences. A particularly high diversity of MTB was observed, with cocci phylogenetically distributed across the order Magnetococcales, including a novel cluster with sequences from the Mediterranean Sea designated as "Med group", and novel morphotypes.

Vallitalea pronyensis sp. nov., isolated from a marine alkaline hydrothermal chimney.

A novel thermotolerant, anaerobic, Gram-stain-positive, spore-forming bacterium was isolated from a hydrothermal chimney in Prony Bay, New Caledonia. This strain, designated FatNI3(T), grew at 15-55 °C (optimum 30 °C) and at pH 5.8-8.9 (optimum 7.7). It was slightly halophilic, requiring at least 0.5 % NaCl for growth (optimum 2.5-3.0 %), and was able to grow at up to 6 % NaCl. Sulfate, thiosulfate, elemental sulfur, sulfite, nitrate and nitrite were not used as terminal electron acceptors. Growth of strain FatNI3(T) was inhibited in the presence of sulfite (2 mM) or nitrite (2 mM). Strain FatNI3(T) fermented cellobiose, glucose, mannose, maltose, sucrose, galactose, lactose, ribose, fructose, rhamnose, raffinose, xylose, yeast extract, peptone and biotrypticase. The main fermentation products from glucose metabolism were acetate, ethanol, H2 and CO2. The predominant cellular fatty acids were iso-C15 : 0 and anteiso-C15 : 0. The main polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, and unknown glycolipids and phospholipids. The G+C content of the genomic DNA was 36.6 mol%. On the basis of phylogenetic and physiological properties, strain FatNI3(T) ( = DSM 25904 = JCM 18391) belonging to the phylum Firmicutes, class Clostridia, order Clostridiales, is proposed as the type strain of a novel species of the genus Vallitalea, for which the name Vallitalea pronyensis sp. nov. is proposed.

Vallitalea guaymasensis gen. nov., sp. nov., isolated from marine sediment.

A novel obligately anaerobic, non-spore-forming, rod-shaped mesophilic, halophilic, Gram-stain-negative bacterium, was isolated from sediments of Guaymas Basin. The strain, designated Ra1766G1(T), grew at 20-40 °C (optimum, 30-35 °C) and at pH 6.0-8.0 (optimum, pH 6.5-7.5). It required 0.5-7.5 % NaCl (optimum, 2-3 %) for growth. Sulfate, thiosulfate, elemental sulfur, sulfite, fumarate, nitrate and nitrite were not used as terminal electron acceptors. Strain Ra1766G1(T) used cellobiose, glucose, mannose, maltose, arabinose, raffinose, galactose, ribose, sucrose, pyruvate and xylose as electron donors. The main fermentation product from glucose metabolism was acetate. The predominant cellular fatty acids were anteiso-C15 : 0, iso-C15 : 0, anteiso DMA-C15 : 0 and C16 : 0. The main polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, iso-DMA-C15 : 0 glycolipids and phospholipids. The G+C content of the genomic DNA was 31.2 mol%. The closest phylogenetic relatives of strain Ra1766G1(T) were Natranaerovirga pectinivora AP3(T) (92.4 % 16S rRNA gene sequence similarity), Natranaerovirga hydrolytica APP2(T)(90.2 %) and Defluviitalea saccharophila 6LT2(T) (88.9 %). On the basis of phylogenetic inference and phenotypic properties, strain Ra1766G1(T) represents a novel species of a new genus for which the name Vallitalea guaymasensis is proposed. The type strain of the type species is Ra1766G1(T) ( = DSM 24848(T) = JCM17997(T)).

Fonticella tunisiensis gen. nov., sp. nov., isolated from a hot spring.

A strictly anaerobic, moderately thermophilic, halotolerant rod, designated BELH25(T), was isolated from a water sample of a Tunisian hot spring. Cells were non-motile, 2-6 µm long and 0.4-0.6 µm wide, appearing singly or in pairs. The isolate grew at 45-70 °C (optimum 55 °C), at pH 6.2-8.0 (optimum pH 7.0) and with 0-4% NaCl (optimum 0-2.0%). Sulfate, thiosulfate, elemental sulfur, sulfite, nitrate and nitrite were not used as terminal electron acceptors. Strain BELH25(T) used cellobiose, fructose, galactose, glucose, maltose, mannose, sucrose, starch and yeast extract as electron donors. The main fermentation products from glucose metabolism were formate, acetate, ethanol and CO2. The predominant cellular fatty acids were iso-C15:0, iso-C17:0 and anteiso-C15:0. The DNA G+C content was 37.2 mol%. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain BELH25(T) was most closely related to Caloramator viterbiensis JW/MS-VS5(T) and Fervidicella metallireducens AeB(T) (92.2 and 92.1% sequence similarity, respectively), and the isolate was positioned approximately equidistantly between these genera. Based on phenotypic, phylogenetic and chemotaxonomic characteristics, strain BELH25(T) is proposed to be a member of a novel species of a novel genus within the order Clostridiales, family Clostridiaceae, for which the name Fonticella tunisiensis gen. nov., sp. nov. is proposed. The type strain of the type species is BELH25(T) (=DSM 24455(T)=JCM 17559(T)).

Isolation and characterization of Desulfocurvus thunnarius sp. nov., a sulfate-reducing bacterium isolated from an anaerobic sequencing batch reactor treating cooking wastewater.

A novel anaerobic, chemo-organotrophic, sulfate-reducing bacterium, designated strain Olac 40(T), was isolated from a Tunisian wastewater digestor. Cells were curved, motile rods or vibrios (5.0-7.0×0.5 µm). Strain Olac 40(T) grew at temperatures between 15 and 50 °C (optimum 40 °C), and between pH 5.0 and 9.0 (optimum pH 7.1). It did not require NaCl for growth but tolerated it up to 50 g l(-1) (optimum 2 g l(-1)). In the presence of sulfate or thiosulfate, strain Olac 40(T) used lactate, pyruvate and formate as energy sources. Growth was observed on H2 only in the presence of acetate as carbon source. In the presence of sulfate or thiosulfate, the end products of lactate oxidation were acetate, sulfide and CO2. Sulfate, thiosulfate and sulfite were used as terminal electron acceptors, but not elemental sulfur, nitrate or nitrite. The genomic DNA G+C content of strain Olac 40(T) was 70 mol%. The profile of polar lipids consisted of phosphatidylglycerol, phosphatidylethanolamine, aminophospholipid and four phospholipids. The main fatty acids were C16 : 0, anteiso-C15 : 0 and iso-C15 : 0. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Olac 40(T) was affiliated with the family Desulfovibrionaceae within the class Deltaproteobacteria. On the basis of 16S rRNA gene sequence comparisons and physiological characteristics, strain Olac 40(T) is proposed to be assigned to a novel species of the genus Desulfocurvus, for which the name Desulfocurvus thunnarius is proposed. The type strain is Olac 40(T) ( = DSM 26129(T) = JCM 18546(T)).

Mesotoga infera sp. nov., a mesophilic member of the order Thermotogales, isolated from an underground gas storage aquifer.

Strain VNs100(T), a novel mesophilic, anaerobic, rod-coccoid-shaped bacterium, having a sheath-like outer structure (toga), was isolated from a water sample collected in the area of an underground gas storage aquifer. It was non-motile with cells appearing singly (2-4 µm long × 1-2 µm wide), in pairs or as long chains and stained Gram-negative. Strain VNs100(T) was heterotrophic, able to use arabinose, cellobiose, fructose, galactose, glucose, lactose, lactate, mannose, maltose, raffinose, ribose, sucrose and xylose as energy sources only in the presence of elemental sulfur as terminal electron acceptor. Acetate, CO2 and sulfide were the end products of sugar metabolism. Hydrogen was not detected. Elemental sulfur, but not thiosulfate, sulfate or sulfite, were reduced to sulfide. Strain VNs100(T) grew at temperatures between 30 and 50 °C (optimum 45 °C), at pH values between 6.2 and 7.9 (optimum 7.3-7.5) and at NaCl concentrations between 0 and 15 g l(-1) (optimum 2 g l(-1)). The DNA G+C content was 47.5 mol%. The main cellular fatty acid was C16 : 0. Phylogenetic analysis of the small subunit rRNA gene sequence indicated that strain VNs100(T) had as its closest relatives 'Mesotoga sulfurireducens' (97.1 % similarity) and Mesotoga prima (similarity of 97.1 % and 97.7 % with each of its two genes, respectively) within the order Thermotogales. Hybridization between strain VNS100(T) and 'M. sulfurireducens' and between strain VNS100(T) and M. prima showed 12.9 % and 20.6 % relatedness, respectively. Based on phenotypic, phylogenetic and taxonomic characteristics, strain VNs100(T) is proposed as a representative of a novel species of the genus Mesotoga in the family Thermotogaceae, order Thermotogales. The name Mesotoga infera sp. nov. is proposed. The type strain is VNs100(T) (= DSM 25546(T) = JCM 18154(T)).

Metabolic challenges and key players in serpentinite-hosted microbial ecosystems.

Serpentinite-hosted systems are amongst the most challenging environments for life on Earth. Serpentinization, a geochemical alteration of exposed ultramafic rock, produces hydrothermal fluids enriched in abiotically derived hydrogen (H2), methane (CH4), and small organic molecules. The hyperalkaline pH of these fluids poses a great challenge for metabolic energy and nutrient acquisition, curbing the cellular membrane potential and limiting electron acceptor, carbon, and phosphorous availability. Nevertheless, serpentinization supports the growth of diverse microbial communities whose metabolic make-up might shed light on the beginning of life on Earth and potentially elsewhere. Here, we outline current hypotheses on metabolic energy production, carbon fixation, and nutrient acquisition in serpentinizing environments. A taxonomic survey is performed for each important metabolic function, highlighting potential key players such as H2 and CH4 cycling Serpentinimonas, Hydrogenophaga, Methanobacteriales, Methanosarcinales, and novel candidate phyla. Methodological biases of the available data and future approaches are discussed.

Microbial taxa related to natural hydrogen and methane emissions in serpentinite-hosted hyperalkaline springs of New Caledonia.

The southeastern part of New Caledonia main island (Grande Terre) is the location of a large ophiolitic formation that hosts several hyperalkaline springs discharging high pH (∼11) and warm (<40°C) fluids enriched in methane (CH4) and hydrogen (H2). These waters are produced by the serpentinization of the ultrabasic rock formations. Molecular surveys had previously revealed the prokaryotic diversity of some of these New Caledonian springs, especially from the submarine chimneys of Prony Bay hydrothermal field. Here we investigate the microbial community of hyperalkaline waters from on-land springs and their relationships with elevated concentrations of dissolved H2 (21.1-721.3 µmol/L) and CH4 (153.0-376.6 µmol/L). 16S rRNA gene analyses (metabarcoding and qPCR) provided evidence of abundant and diverse prokaryotic communities inhabiting hyperalkaline fluids at all the collected springs. The abundance of prokaryotes was positively correlated to the H2/CH4 ratio. Prokaryotes consisted mainly of bacteria that use H2 as an energy source, such as microaerophilic Hydrogenophaga/Serpentinimonas (detected in all sources on land) or anaerobic sulfate-reducing Desulfonatronum, which were exclusively found in the most reducing (Eh ref H2 ∼ -700 mV) and the most H2-enriched waters discharging at the intertidal spring of the Bain des Japonais. The relative abundance of a specific group of uncultured Methanosarcinales that thrive in serpentinization-driven ecosystems emitting H2, considered potential H2-consuming methanogens, was positively correlated with CH4 concentrations, and negatively correlated to the relative abundance of methylotrophic Gammaproteobacteria. Firmicutes were also numerous in hyperalkaline waters, and their relative abundance (e.g., Gracilibacter or Dethiobacter) was proportional to the dissolved H2 concentrations, but their role in the H2 budget remains to be assessed. The prokaryotic communities thriving in New Caledonia hyperalkaline waters are similar to those found in other serpentinite-hosted high-pH waters worldwide, such as Lost City (North Atlantic) and The Cedars (California).