Anaerobaca lacustris gen. nov., sp. nov., an obligately anaerobic planctomycete of the widespread SG8-4 group, isolated from a coastal lake, and proposal of Anaerobacaceae fam. nov.

One of the numerous and widespread lineages of planctomycetes is the hitherto uncultured SG8-4 group inhabiting anoxic environments. A novel anaerobic, mesophilic, alkalitolerant, chemoorganotrophic bacterium (strain M17dextrT) was isolated from anaerobic sediment of a coastal lake (Taman Peninsula, Russia). The cell were mainly non-motile cocci, 0.3 to 1.0 µm in diameter forming chains or aggregates. The cells had a Gram-negative cell wall and divided by binary fission. The temperature range for growth was 20-37 0C (optimum at 30 0C). The pH range for growth was 6.5-10.0, with an optimum at pH 8.0-8.5. Strain M17dextrT fermented mono-, di- and polysaccharides (starch, xanthan gum, dextran, N-acetylglucosamine), but did not utilized proteinaceous compounds. Major cellular fatty acids were C16:0 and C18:0. The genome of strain M17dextrT had a size of 5.7 Mb with a G + C content of 62.49 %. The genome contained 345 CAZyme genes. The closest cultured phylogenetic relatives of strain M17dextrT were members of the order Sedimentisphaerales, class Phycisphaerae. Among characterized planctomycetes, the highest 16S rRNA gene sequence similarity (88.3 %) was observed with Anaerohalosphaera lusitana. According to phylogenomic analysis strain M17dextrT together with many uncultured representatives of Sedimentisphaerales forms a separate family-level lineage. We propose to assign strain M17dextrT to a novel genus and species, Anaerobaca lacustris gen. nov., sp. nov.; the type strain is M17dextrT (=VKM B-3571 T = DSM 113417 T = JCM 39238 T = KCTC 25381 T = UQM 41474 T). This genus is placed in a novel family, Anaerobacaceae fam. nov. within the order Sedimentisphaerales.

Desulfatitalea alkaliphila sp. nov., an alkalipilic sulfate- and arsenate- reducing bacterium isolated from a terrestrial mud volcano.

A novel alkaliphilic sulfate-reducing bacterium, strain M08butT, was isolated from a salsa lake of terrestrial mud volcano (Taman Peninsula, Russia). Cells were rod-shaped, motile and Gram-stain-negative. The temperature range for growth was 15-42 °C (optimum at 30 °C). The pH range for growth was 7.0-11.0, with an optimum at pH 8.5-9.0 Strain M08butT used sulfate, thiosulfate, sulfite, dimethyl sulfoxide and arsenate as electron acceptors. Acetate, formate, butyrate, fumarate, succinate, glycerol and pyruvate were utilized as electron donors with sulfate. Fermentative growth was observed with fumarate, pyruvate, crotonate. Strain M08butT grew chemolithoautotrophically with H2 and CO2. The G + C content of the genomic DNA was 60.1%. The fatty acid profile of strain M08butT was characterized by the presence of anteiso-C15:0 as the major component (68.8%). The closest phylogenetic relative of strain M08butT was Desulfatitalea tepidiphila (the order Desulfobacterales) with 96.3% 16S rRNA gene sequence similarity. Based on the phenotypic, genotypic and phylogenetic characteristics of the isolate, strain M08butT is considered to represent a novel species of the genus Desulfatitalea, with proposed name Desulfatitalea alkaliphila sp. nov. The type strain of Desulfatitalea alkaliphila is M08butT (= KCTC 25382T = VKM B-3560T = DSM 113909T = JCM 39202T = UQM 41473T).

Moorella sulfitireducens sp. nov., a thermophilic anaerobic bacterium isolated from a terrestrial thermal spring.

In hydrothermal ecosystems, the dissolution of sulfur dioxide in water results in the formation of sulfite, which can be used in microbial metabolism. A limited number of thermophiles have been isolated using sulfite as an electron acceptor. From a terrestrial thermal spring, Sakhalin Island, Russia, we isolated a thermophilic anaerobic bacterium (strain SLA38T). Cells of strain SLA38T were spore-forming straight rods. Growth was observed at temperatures 45-65 °C (optimum at 60 °C) and pH 5.5-9.0 (optimum at pH 6.5-7.0). The novel isolate was capable of anaerobic respiration with sulfite, thiosulfate, fumarate and perchlorate or fermentative growth. Strain SLA38T utilized glycerol, lactate, pyruvate and yeast extract. It grew lithoautotrophically on carbon monoxide with thiosulfate as electron acceptor, producing acetate. The genome size of the isolate was 2.9 Mbp and genomic DNA G + C content was 53.6 mol%. Analysis of the 16S rRNA gene sequences revealed that strain SLA38T belongs to the genus Moorella. Based on the physiological features and phylogenetic analysis, we propose to assign strain SLA38T to a new species of the genus Moorella, as Moorella sulfitireducens sp. nov. The type strain is SLA38T (= DSM 111068T = VKM B-3584T).

Pelovirga terrestris gen. nov., sp. nov., anaerobic, alkaliphilic, fumarate-, arsenate-, Fe(III)- and sulfur-reducing bacterium isolated from a terrestrial mud volcano.

A novel anaerobic, mesophilic, alkaliphilic, chemoorganotrophic bacterium (strain M08fumT) was isolated from a salsa lake of a terrestrial mud volcano (Taman Peninsula, Russia). Cell of strain M08fumT were Gram-stain-negative, rod-shaped, non-spore forming motile rods. The temperature range for growth was 10-45 °C (optimum at 30 °C). The pH range for growth was 7.0-11.0, with an optimum at pH 8.5-9.0. The isolate was capable of organic acids fermentation and anaerobic respiration with elemental sulfur, Fe(III) and arsenate. The end products of fumarate fermentation were succinate, acetate and CO2. The closest phylogenetic relatives of strain M08fumT were members of the family Geopsychrobacteraceae, class Desulfuromonadia. The genome of strain M08fumT had a size of 3.10 Mb with a DNA G + C content of 53.1% (WGS). Genome analysis revealed the presence of genes involved in fumarate fermentation, arsenate reduction and resistance, sulfur respiration and Fe (III) reduction. Based on the phenotypic, genotypic and phylogenetic characteristics we propose to assign strain M08fumT to a new species of a novel genus Pelovirga terrestris gen. nov., sp. nov. within the family Geopsychrobacteraceae. The type strain of Pelovirga terrestris is M08fumT (=KCTC 15919T = VKM B-3407T). This is the first representative of the class Desulfuromonadia, isolated in pure culture from a mud volcano and the first alkaliphile in the family Geopsychrobacteraceae.

Perlabentimonas gracilis gen. nov., sp. nov., a gliding aerotolerant anaerobe of the order Bacteroidales, isolated from a terrestrial mud volcano.

A novel anaerobic bacterium (strain M08_MBT) was isolated from a terrestrial mud volcano (Taman Peninsula, Russia). Gram-stain-negative cells were straight and slender rods with gliding motility, occasionally forming long filaments. The isolate was mesophilic, slightly halo- and alkaliphilic chemoorganoheterotroph, growing on carbohydrates (starch, dextrin, pectin, glucose, fructose, mannose, maltose, trehalose, lactose, sucrose) and proteinaceous compounds (peptone, tryptone, gelatin, casein and albumin). Strain M08_MBT tolerated 3% oxygen in the gas phase while catalase negative. The dominant cellular fatty acids of strain M08_MBT were C15:0, C15:1 and C13:0 acids. 16S rRNA gene sequence analysis revealed that strain M08_MBT belongs to the order Bacteroidales and only distantly related to other cultivated members of this order (85.12-90.01% 16S rRNA gene similarity). The genome of strain M08_MBT had a size of 4.37 Mb with a DNA G + C content of 43.5 mol% (WGS). The genes involved in gliding motility, proteolysis, central carbon metabolism, and oxygen tolerance were listed in genome annotation. Based on the phenotypic and genotypic characteristics, strain M08_MBT represents a novel species of a novel genus within family Tenuifilaceae, with proposed name Perlabentimonas gracilis gen. nov., sp. nov. The type strain is M08_ MBT (=DSM 110720 T = VKM B-3471 T). This is the first representative of Bacteroidales isolated in pure culture from a mud volcano.

Pseudodesulfovibrio alkaliphilus, sp. nov., an alkaliphilic sulfate-reducing bacterium isolated from a terrestrial mud volcano.

The diversity of anaerobic microorganisms in terrestrial mud volcanoes is largely unexplored. Here we report the isolation of a novel sulfate-reducing alkaliphilic bacterium (strain F-1T) from a terrestrial mud volcano located at the Taman peninsula, Russia. Cells of strain F-1T were Gram-negative motile vibrios with a single polar flagellum; 2.0-4.0 µm in length and 0.5 µm in diameter. The temperature range for growth was 6-37 °C, with an optimum at 24 °C. The pH range for growth was 7.0-10.5, with an optimum at pH 9.5. Strain F-1T utilized lactate, pyruvate, and molecular hydrogen as electron donors and sulfate, sulfite, thiosulfate, elemental sulfur, fumarate or arsenate as electron acceptors. In the presence of sulfate, the end products of lactate oxidation were acetate, H2S and CO2. Lactate and pyruvate could also be fermented. The major product of lactate fermentation was acetate. The main cellular fatty acids were anteiso-C15:0, C16:0, C18:0, and iso-C17:1ω8. Phylogenetic analysis revealed that strain F-1T was most closely related to Pseudodesulfovibrio aespoeensis (98.05% similarity). The total size of the genome of the novel isolate was 3.23 Mb and the genomic DNA G + C content was 61.93 mol%. The genome contained all genes essential for dissimilatory sulfate reduction. We propose to assign strain F-1T to the genus Pseudodesulfovibrio, as a new species, Pseudodesulfovibrio alkaliphilus sp. nov. The type strain is F-1T (= KCTC 15918T = VKM B-3405T).

Anaerotalea alkaliphila gen. nov., sp. nov., an alkaliphilic, anaerobic, fermentative bacterium isolated from a terrestrial mud volcano.

Diversity of extremophilic microorganisms in mud volcanoes is largely unexplored. Here, we report the isolation of a novel alkaliphilic, mesophilic, fermentative bacterium (strain F-3apT) from a terrestrial mud volcano located at the Taman peninsula, Russia. Cells of strain F-3apT are Gram-stain-positive non-motile rods. The formation of endospores is not observed. The temperature range for growth is 14-42 °C, with an optimum at 37 °C. The pH range for growth is 7.5-11.0, with an optimum at pH 9.0. The isolate utilizes various organic polymeric substances, organic acids, carbohydrates, and proteinaceous compounds. The end products of glucose fermentation are ethanol, CO2, and H2. The major cellular fatty acids of strain F-3apT are C16:0, C16:1, and C14:0. Phylogenetic analysis reveals that strain F-3apT belongs to the order Clostridiales, with less than 91% of 16S rRNA gene sequence similarity to any species with a validly published name. The total size of the genome of strain F-3apT is 2.98 Mb, and a genomic DNA G + C content is 56.78 mol%. The whole-genome phylogenetic analysis confirms that strain F-3apT forms a distinct lineage within Clostridia. We propose to assign strain F-3apT to a new species of a novel genus Anaerotalea alkaliphila gen. nov., sp. nov. The type strain is F-3apT (= KCTC 15917 T = VKM B-3406 T).

Alkalibaculum sporogenes sp. nov., isolated from a terrestrial mud volcano and emended description of the genus Alkalibaculum.

A novel anaerobic, endospore-forming bacterium (strain M08 DMBT) was isolated from a terrestrial mud volcano (Taman Peninsula, Russia). Cells of the strain were motile rods 1.3-2.0 µm long and 0.4 µm in diameter. The temperature range for growth was 5-42 °C, with an optimum at 30 °C. The pH range for growth was H 6.5-11.0, with an optimum at pH 8.0. Growth of strain M08 DMBT was observed at NaCl concentrations of 0-5.0 % (w/v) with an optimum at 1.0 %. Strain M08 DMBT utilized 3,4-dimethoxybenzoic acid, 2-methoxyphenol, carbon monoxide, glucose, fructose, mannose, xylose and yeast extract. The end product of glucose fermentation was acetate. The DNA G+C content of strain M08 DMBT was 32.3 mol% (obtained via whole genome sequencing). The closest phylogenetic relative of strain M08 DMBT was Alkalibaculum bacchi (family Eubacteriaceae, class Clostridia) with 95.17 % 16S rRNA gene sequence similarity. Based on the phenotypic, genotypic and phylogenetic characteristics of the isolate, strain M08 DMBT is considered to represent a novel species of the genus Alkalibaculum, for which the name Alkalibaculum sporogenes sp. nov. is proposed. The type strain of Alkalibaculum sporogenes is M08 DMBT (=KCTC 15840T=VKM B-3387T).

Calorimonas adulescens gen. nov., sp. nov., an anaerobic thermophilic bacterium utilizing methoxylated benzoates.

A novel anaerobic, thermophilic bacterium (strain A05 MBT) was isolated from Daginsky thermal springs (Sakhalin, Russia) on 2-methoxybenzoate as a substrate. Cells of the strain were motile long rods, 3.0-5.0 µm in length and 0.5-0.6 µm in diameter. The temperature range for growth was 47-68 °C, with an optimum at 60 °C. The pH range for growth was 4.5-8.0, with an optimum at pH 5.5-6.0. Strain A05 MBT did not require NaCl for growth. The strain utilized methoxylated aromatic compounds (2-methoxybenzoate and 3,4-dimethoxybenzoate), a number of carbohydrates (glucose, fructose, mannose, trehalose, xylose, sucrose, galactose, ribose, maltose, raffinose, lactose, cellobiose and dextrin) and proteinaceous substrates (yeast extract, beef extract, peptone and tryptone). The end products of glucose fermentation were acetate, ethanol and CO2. The DNA G+C content of strain A05 MBT was 40.2 mol% (whole-genome analysis). 16S rRNA gene sequence analysis revealed that strain A05MBT belongs to the order Thermoanaerobacterales (phylum Firmicutes). The closest relative of strain A05 MBT was Caloribacterium cisternae (94.3 % 16S rRNA gene sequence similarity). Based on the phenotypic, genotypic and phylogenetic characteristics of the isolate, strain A05 MBT is considered to represent a novel species of a new genus, for which the name Calorimonas adulescens gen. nov., sp. nov. is proposed. The type strain of Calorimonas adulescens is A05 MBT (=KCTC 15839T=VKM B-3388T).

Sulfurimonas crateris sp. nov., a facultative anaerobic sulfur-oxidizing chemolithoautotrophic bacterium isolated from a terrestrial mud volcano.

A novel mesophilic facultative anaerobic bacterium, strain SN118T, was isolated from a terrestrial mud volcano in Taman Peninsula, Russia. The cells were Gram-negative, motile, short, straight or curved rods with a single polar flagellum. Growth was observed at 5-40 °C (optimum, 30 °C) and pH 5.5-9.5 (optimum, pH 8.0). Growth of strain SN118T was observed in NaCl concentrations ranging from 0.5 to 8.0 % (w/v) with an optimum at 2.0-3.0 % (w/v). The isolate grew chemolithoautotrophically with sulfide, elemental sulfur or thiosulfate as electron donor, oxygen, nitrate or nitrite as an electron acceptor and CO2/HCO3 - as a carbon source. Molecular hydrogen or organic substances did not support growth. Nitrate was reduced to N2. The dominant fatty acids were C16 : 1ω7c, C16 : 0 and C18  :  1ω7c. The total size of the genome of the novel isolate was 2 209 279 bp and the genomic DNA G+C content was 38.8 mol%. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel isolate belonged to the genus Sulfurimonas and was most closely related to Sulfurimonas denitrificans DSM 1251T (96.74 %). Based on its physiological properties and results from phylogenetic analyses, including average nucleotide identity and in silico DNA-DNA hybridization values, the isolate is considered to represent a novel species of the genus Sulfurimonas, for which the name Sulfurimonas crateris sp. nov. is proposed. The type strain is SN118T (=DSM 109248T=VKM B-3378T).

Pelomicrobium methylotrophicum gen. nov., sp. nov. a moderately thermophilic, facultatively anaerobic, lithoautotrophic and methylotrophic bacterium isolated from a terrestrial mud volcano.

A novel moderately thermophilic, bacterium, strain SM250T, was isolated from a terrestrial mud volcano, Taman peninsula, Krasnodar region, Russia. Cells of strain SM250T were Gram-negative non-spore forming motile straight rods. Growth was observed at temperatures 30-63 °C (optimum at 50 °C), pH 6.5-10.0 (optimum at pH 8.5) and NaCl concentrations 0-4.5% (w/v) (optimum at 1.0-1.5% (w/v)). The novel isolate grows by aerobic respiration or anaerobic respiration with nitrate as the terminal electron acceptor. Strain SM250T grows by the utilization of methanol, formate and a number of other organic compounds or lithoautotrophically with hydrogen, elemental sulfur or thiosulfate as electron donors. The total size of the genome of the novel isolate was 3,327,116 bp and a genomic DNA G + C content was 64.8 mol%. Analysis of the 16S rRNA gene sequences revealed that strain SM250T belongs to the class Hydrogenophilia within the phylum Proteobacteria, with less than 91% of 16S rRNA gene sequence similarity to any species with validly published name. We propose to assign strain SM250T to a new species of a novel genus Pelomicrobium methylotrophicum gen. nov., sp. nov. The type strain is SM250T (= KCTC 62861T = VKM B-3274T).

Tepidibaculum saccharolyticum gen. nov., sp. nov. a moderately thermophilic, anaerobic, spore-forming bacterium isolated from a terrestrial hot spring.

A novel moderately thermophilic, anaerobic bacterium, strain STR9T was isolated from terrestrial hot spring at Uzon Caldera, Kamchatka peninsula, Russia. Cells of strain STR9T were spore-forming motile straight or slightly curved rods 0.3 µm in diameter and 1.0-2.0 µm in length having a Gram-positive cell-wall structure. The temperature range for growth was 30-58 °C, with an optimum at 50 °C. The pH range for growth was 5.0-10.5, with an optimum at pH 8.0-9.0. NaCl inhibited growth of the strain STR9T and no growth was evident above 0.5% NaCl (w/v). Several mono-, di-, and polysaccharides as well as beef extract and yeast extract supported growth. The main end products of glucose fermentation were ethanol, acetate, hydrogen, and carbon dioxide. The G + C content of DNA of strain STR9T was 40.0 mol% (Tm). Analysis of the 16S rRNA gene sequences revealed that strain STR9T belongs to the family Ruminococcaceae, class Clostridia, with less than 93% 16S rRNA gene sequence similarity to any species with validly published name. We propose to assign strain STR9T to a new species of a novel genus Tepidibaculum saccharolyticum gen. nov., sp. nov. The type strain is STR9T (= DSM 28577T = VKM B-2882T = UNIQEM STR9T).

Thermodesulfitimonas autotrophica gen. nov., sp. nov., a thermophilic, obligate sulfite-reducing bacterium isolated from a terrestrial hot spring.

A novel thermophilic, anaerobic, chemolithoautotrophic bacterium, strain SF97T, was isolated from a terrestrial hot spring (Kuril Islands, Russia). Cells of strain SF97T were rod-shaped and motile with a Gram-positive cell-wall type. The novel isolate grew at 45-72 °C (optimum 65 °C) and pH 5.5-8.5 (optimum 6.0-6.5). The strain grew chemolithoautotrophically with molecular hydrogen as an electron donor, sodium sulfite or SO2 gas as an electron acceptor and bicarbonate/CO2 as a carbon source. Sulfate, thiosulfate, elemental sulfur, Fe(III) or nitrate were not used as electron acceptors either with H2 or organic electron donors. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belonged to the family Thermoanaerobacteraceae, order Thermoanaerobacterales, and was distantly related to species of the genus Ammonifex (92-93 % sequence similarity). On the basis of its physiological properties and results of phylogenetic analyses, strain SF97T is considered to represent a novel species of a new genus, for which the name Thermodesulfitimonas autotrophica gen. nov., sp. nov. is proposed. The type strain of Thermodesulfitimonas autotrophica is SF97T (=DSM 102936T=VKM B-2961T). T. autotrophica is the first reported obligate sulfite-reducing micro-organism.

Dissulfurimicrobium hydrothermale gen. nov., sp. nov., a thermophilic, autotrophic, sulfur-disproportionating deltaproteobacterium isolated from a hydrothermal pond.

A thermophilic, anaerobic, chemolithoautotrophic bacterium (strain Sh68T) was isolated from a hydrothermal pond at Uzon Caldera, Kamchatka, Russia, using anoxic medium with elemental sulfur as the only energy source. Cells of strain Sh68T were Gram-stain-negative rods, 0.5-0.8 µm in diameter and 1.2-2.0 µm in length, motile by means of flagella. The temperature range for growth was 30-65 °C, with an optimum at 50-52 °C. The pH range for growth was 5.2-7.5, with optimum growth at pH 6.0-6.2. Growth of strain Sh68T was observed at NaCl concentrations ranging from 0 to 2.3 % (w/v). Strain Sh68T grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO2 as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. Growth was enhanced in the presence of poorly crystalline Fe(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain Sh68T was also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor either with H2 or with organic electron donors. Analysis of the 16S rRNA gene sequence revealed that the isolate belongs to the class Deltaproteobacteria and is related most closely to Dissulfuribacter thermophilus S69T (90.0 % similarity). On the basis of its physiological properties and results of phylogenetic analyses, strain Sh68T is considered to represent a novel species of a new genus, for which the name Dissulfurimicrobium hydrothermale gen. nov., sp. nov. is proposed. The type strain of Dissulfurimicrobium hydrothermale is Sh68T ( = JCM 19990T = VKM B-2854T). This is the first description of a sulfur-disproportionating thermophile from a terrestrial ecosystem.

Pyrobaculum ferrireducens sp. nov., a hyperthermophilic Fe(III)-, selenate- and arsenate-reducing crenarchaeon isolated from a hot spring.

A novel hyperthermophilic, anaerobic, archaeon was isolated from a terrestrial hot spring at Uzon Caldera, Kronotsky Nature Reserve, Kamchatka, Russia. The isolate, strain 1860(T), grew optimally at 90-95 °C and pH 6.0-7.0. The cells were non-motile straight rods, 1.5-5.0 µm in length, covered with surface-layer lattice. Strain 1860(T) utilized complex proteinaceous compounds as electron donors and ferrihydrite, Fe(III) citrate, nitrate, thiosulfate, selenite, selenate and arsenate as electron acceptors for growth. The sequence of the 16S rRNA gene of strain 1860(T) had 97.9-98.7 % similarity with those of members of the genus Pyrobaculum. On the basis of its physiological properties and phylogenetic analyses including in silico genome to genome hybridization, the isolate is considered to represent a novel species, for which the name Pyrobaculum ferrireducens sp. nov. is proposed. The type strain is 1860(T) ( = DSM 28942(T) = VKM B-2856(T)).

[Thermophilic prokaryotes from deep subterranean habitats].

The deep continental biosphere consists of geologically isolated ecosystems differing in their physicochemical, geological, and trophic parameters. Most of the deep ecosystems exist at elevated temperatures (50-120 degrees C), which favor the development of thermophilic microorganisms. In many cases, indigenous nature of subsurface microorganisms is questionable due to problems of collecting representative and non-contaminated samples. In spite of the numerous studies on the deep biosphere microbial communities, the number of cultivated thermophiles isolated from subsurface environments not associated with petroleum deposits does not exceed 30 species. More than half of the thermophilic species isolated from deep subsurface belong to the Firmicutes. Majority of the underground thermophiles are subsurface strict or facultative anaerobes, with capacity for sulfate and iron reduction are notably widespread. Most thermophilic subsurface microorganisms are organotrophs, although chemolithoautotrophic thermophiles also have been reported. This review deals with the phylogenetic diversity and physiological properties of the cultivated thermophilic prokaryotes isolated from various deep subterranean habitats.

Tepidibacillus fermentans gen. nov., sp. nov.: a moderately thermophilic anaerobic and microaerophilic bacterium from an underground gas storage.

A novel moderately thermophilic bacterium, strain STGH(T), was isolated from Severo-Stavropolskoye underground gas storage (Russia). Cells of strain STGH(T) were spore-forming motile straight rods 0.3 µm in diameter and 2.0-4.0 µm in length having a Gram-positive cell wall structure. The temperature range for growth was 36-65 °C, with an optimum at 50-52 °C. The pH range for growth was 5.5-8.0, with an optimum at pH 7.0-7.5. Growth of strain STGH(T) was observed at NaCl concentrations ranging from 0 to 4.0 % (w/v) with an optimum at 1.0 % (w/v). Strain STGH(T) grew anaerobically by reduction of nitrate, thiosulfate, S(0) and AQDS using a number of complex proteinaceous compounds, organic acids and carbohydrates as electron donors. Nitrate was reduced to nitrite; thiosulfate and sulfur were reduced to sulfide. It also was able to ferment pyruvate, glucose, fructose, and maltose. The strain STGH(T) did not grow under aerobic conditions during incubation with atmospheric concentration of oxygen but was able to microaerobic growth (up to 10 % of oxygen in gas phase). The G+C content of DNA of strain STGH(T) was 34.8 mol%. 16S rRNA gene sequence analysis revealed that the isolated organism belongs to the class Bacilli. We propose to assign strain STGH(T) to a new species of a novel genus Tepidibacillus fermentans gen. nov., sp.nov. The type strain is STGH(T) (=DSM 23802(T), =VKM B-2671(T)).

Dissulfuribacter thermophilus gen. nov., sp. nov., a thermophilic, autotrophic, sulfur-disproportionating, deeply branching deltaproteobacterium from a deep-sea hydrothermal vent.

A thermophilic, anaerobic, chemolithoautotrophic bacterium (strain S69(T)) was isolated from a deep-sea hydrothermal vent chimney located on the Eastern Lau Spreading Center and Valu Fa Ridge, Pacific Ocean, at a depth of 1910 m using anoxic medium with elemental sulfur as the only energy source. Cells of strain S69(T) were Gram-negative short rods, 0.4-0.6 µm in diameter and 1.0-2.5 µm in length, motile with a single polar flagellum. The temperature range for growth was 28-70 °C, with an optimum at 61 °C. The pH range for growth was 5.6-7.9, with optimum growth at pH 6.8. Growth of strain S69(T) was observed at NaCl concentrations ranging from 0.9 to 5.0%, with an optimum at 1.8-2.7 (w/v). Strain S69(T) grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO2 as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. Growth was enhanced in the presence of poorly crystalline Fe(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain S69(T) was also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor either with H2 or with organic electron donors. Analysis of the 16S rRNA gene sequence revealed that the isolate formed a distinct phylogenetic branch within the Deltaproteobacteria. On the basis of its physiological properties and results of phylogenetic analyses, strain S69(T) is considered to represent a novel species of a new genus, for which the name Dissulfuribacter thermophilus gen. nov., sp. nov. is proposed. The type strain of Dissulfuribacter thermophilus is S69(T) (=DSM 25762(T)=VKM B-2760(T)).

Moorella humiferrea sp. nov., a thermophilic, anaerobic bacterium capable of growth via electron shuttling between humic acid and Fe(III).

An anaerobic, thermophilic, spore-forming bacterium (strain 64-FGQ(T)) was isolated from a terrestrial hydrothermal spring from the Kamchatka peninsula, Russia. This strain utilized lactate as an electron donor, insoluble poorly crystalline Fe(III) oxide incorporated into alginate beads as a potential electron acceptor and 9,10-anthraquinone-2,6-disulfonate (AQDS) as an electron-shuttling compound. Vegetative cells of strain 64-FGQ(T) were Gram-stain-positive, peritrichously flagellated, motile, straight rods, 0.3-0.5 µm in diameter and 2.0-5.0 µm long, growing singly or forming short chains. Cells formed round refractive endospores in terminal swollen sporangia. The temperature range for growth was 46-70 °C, with an optimum at 65 °C. The pH range for growth was 5.5-8.5, with an optimum at pH 7.0. The substrates utilized by strain 64-FGQ(T) in the presence of AQDS as an electron acceptor included lactate, malate, succinate, glycerol and yeast extract. The strain fermented galactose, fructose, maltose, sucrose, pyruvate and peptone. Strain 64-FGQ(T) used AQDS, humic acid, thiosulfate, nitrate and perchlorate as electron acceptors for growth. Fe(III) was not directly reduced, but strain 64-FGQ(T) was able to grow and reduce Fe(III) oxide in the presence of small amounts of AQDS or humic acid as electron-shuttling compounds. The G+C content of the DNA of strain 64-FGQ(T) was 51 mol%. 16S rRNA gene sequence analysis placed the isolate in the genus Moorella, with the type strain of Moorella glycerini as its closest relative (97.2% similarity). Based on phylogenetic analysis and physiological characteristics, strain 64-FGQ(T) is considered to represent a novel species of the genus Moorella, for which the name Moorella humiferrea sp. nov. is proposed; the type strain is 64-FGQ(T) (=DSM 23265(T)=VKM B-2603(T)).

Caloribacterium cisternae gen. nov., sp. nov., an anaerobic thermophilic bacterium from an underground gas storage reservoir.

A novel anaerobic, moderately thermophilic bacterium (strain SGL43(T)) was isolated from Severo-Stavropolskoye underground gas storage reservoir (Russia). Cells of strain SGL43(T) were motile straight rods, 0.4 µm in diameter and 2.0-3.0 µm in length. The temperature range for growth was 28-65 °C, with optimum growth at 50 °C. The pH range for growth was 5.5-8.0, with optimum growth at pH 7.0-7.5. Growth of strain SGL43(T) was observed at NaCl concentrations of 0-4.0% (w/v) with optimum growth at 1.0% (w/v) NaCl. Substrates utilized by strain SGL43(T) included peptone, yeast extract, glucose, fructose, maltose, galactose, pyruvate and citrate. Products of glucose or citrate fermentation were acetate, hydrogen and CO(2). Thiosulfate was reduced to sulfide. The DNA G+C content of strain SGL43(T) was 43.1 mol%. 16S rRNA gene sequence analysis revealed that strain SGL43(T) belongs to the order Thermoanaerobacterales (phylum 'Firmicutes'). The closest relative of strain SGL43(T) was Thermoanaerobacterium saccharolyticum (86.2% 16S rRNA gene sequence similarity with the type strain). Based on the data presented here, strain SGL43(T) is considered to represent a novel species of a new genus, for which the name Caloribacterium cisternae gen. nov., sp. nov. is proposed. The type strain of Caloribacterium cisternae, the type species of the genus, is SGL43(T) (=DSM 23830(T)=VKM B-2670(T)).