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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).

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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).

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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).

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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.

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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.

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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)).

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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.

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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)).

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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)).

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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)).

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A thermophilic, anaerobic, dissimilatory Mn(IV)- and Fe(III)-reducing bacterium (strain SLM 61T) was isolated from a terrestrial hot spring on the Kamchatka peninsula. The cells were straight rods, 0.5-0.6 µm in diameter and 1.0-6.0 µm long, and exhibited tumbling motility by means of peritrichous flagellation. The strain grew at 26-70 °C, with an optimum at 58-60 °C, and at pH 5.5-8.0, with an optimum at pH 6.5. Growth of SLM 61T was observed at 0-2.0 % (w/v) NaCl, with an optimum at 0.5 % (w/v). The generation time under optimal growth conditions was 40 min. Strain SLM 61T grew and reduced Mn(IV), Fe(III) or nitrate with a number of organic acids and complex proteinaceous compounds as electron donors. It was capable of chemolithoautotrophic growth using molecular hydrogen as an electron donor, Fe(III) but not Mn(IV) or nitrate as an electron acceptor and CO2 as a carbon source. It also was able to ferment pyruvate, yeast extract, glucose, fructose, sucrose and maltose. The G+C content of DNA of strain SLM 61T was 50.9 mol%. 16S rRNA gene sequence analysis revealed that the closest relative of the isolated organism was Carboxydocella thermautotrophica 41T (96.9 % similarity). On the basis of its physiological properties and phylogenetic analyses, the isolate is considered to represent a novel species, for which the name Carboxydocella manganica sp. nov. is proposed. The type strain is SLM 61T (=DSM 23132T=VKM B-2609T). C. manganica is the first described representative of the genus Carboxydocella that possesses the ability to reduce metals and does not utilize CO.

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An extremely thermophilic, anaerobic, chemolithoautotrophic bacterium (strain S95(T)) was isolated from a deep-sea hydrothermal vent chimney located on the Eastern Lau Spreading Center, Pacific Ocean, at a depth of 1910 m. Cells of strain S95(T) were oval to short Gram-negative rods, 0.5-0.6 µm in diameter and 1.0-1.5 µm in length, growing singly or in pairs. Cells were motile with a single polar flagellum. The temperature range for growth was 50-92 °C, with an optimum at 74 °C. The pH range for growth was 5.5-8.0, with an optimum at pH 7.0. Growth of strain S95(T) was observed at NaCl concentrations ranging from 1.5 to 3.5% (w/v). Strain S95(T) grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO(2) as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. Growth was enhanced in the presence of poorly crystalline iron(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain S95(T) was also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor. Analysis of the 16S rRNA gene sequence revealed that the isolate belongs to the phylum Thermodesulfobacteria. On the basis of its physiological properties and results of phylogenetic analyses, it is proposed that the isolate represents the sole species of a new genus, Thermosulfurimonas dismutans gen. nov., sp. nov.; S95(T) (=DSM 24515(T)=VKM B-2683(T)) is the type strain of the type species. This is the first description of a thermophilic micro-organism that disproportionates elemental sulfur.

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A moderately thermophilic, anaerobic, dissimilatory iron(III)-reducing bacterium (strain S3R1(T)) was isolated from a deep-sea hydrothermal vent chimney located on the Eastern Lau Spreading Centre in the Pacific Ocean at a depth of about 2150 m. Cells of strain S3R1(T) were ovals to short rods with a single polar flagellum, Gram-stain-negative, 0.5-0.6 µm in diameter and 0.8-1.3 µm long, growing singly or in pairs. The temperature range for growth was 36-62 °C, with an optimum at 50 °C. The pH range for growth was 5.5-7.5, with an optimum at pH 6.5. Growth of strain S3R1(T) was observed at NaCl concentrations ranging from 1.0 to 5.0 % (w/v), with an optimum at 2.0-2.5 % (w/v). The isolate used acetate, fumarate, malate, maleinate, succinate, propanol, palmitate, stearate, peptone and yeast extract as electron donors for growth and iron(III) reduction. All electron donors were oxidized completely to CO(2) and H(2)O. Iron(III) (in the form of ferrihydrite, ferric citrate or ferric nitrilotriacetate) and elemental sulfur (S(0)) were the electron acceptors that supported growth. The DNA G+C content was 64.4 mol%. Results of 16S rRNA gene sequence analysis showed that the novel bacterium was related to representatives of the orders Desulfuromonadales and Syntrophobacterales with 84-86 % sequence similarity and formed a distinct phylogenetic branch in the Deltaproteobacteria. On the basis of its physiological properties and results of phylogenetic analyses, it is proposed that the new isolate represents the sole species of a novel genus, Deferrisoma camini gen. nov., sp. nov. The type strain of Deferrisoma camini is S3R1(T) ( = DSM 24185(T)  = VKM B-2672(T)).

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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)).

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A hyperthermophilic, anaerobic, dissimilatory Fe(III)-reducing, facultatively chemolithoautotrophic archaeon (strain SBH6(T)) was isolated from a hydrothermal sample collected from the deepest of the known World Ocean hydrothermal fields, Ashadze field (1 degrees 58' 21'' N 4 degrees 51' 47'' W) on the Mid-Atlantic Ridge, at a depth of 4100 m. The strain was enriched using acetate as the electron donor and Fe(III) oxide as the electron acceptor. Cells of strain SBH6(T) were irregular cocci, 0.3-0.5 mum in diameter. The temperature range for growth was 50-85 degrees C, with an optimum at 81 degrees C. The pH range for growth was 5.0-7.5, with an optimum at pH 6.8. Growth of SBH6(T) was observed at NaCl concentrations ranging from 1 to 6 % (w/v) with an optimum at 2.5 % (w/v). The isolate utilized acetate, formate, pyruvate, fumarate, malate, propionate, butyrate, succinate, glycerol, stearate, palmitate, peptone and yeast extract as electron donors for Fe(III) reduction. It was also capable of growth with H(2) as the sole electron donor, CO(2) as a carbon source and Fe(III) as an electron acceptor without the need for organic substances. Fe(III) [in the form of poorly crystalline Fe(III) oxide or Fe(III) citrate] was the only electron acceptor that supported growth. 16S rRNA gene sequence analysis revealed that the closest relative of the isolated organism was Geoglobus ahangari 234(T) (97.0 %). On the basis of its physiological properties and phylogenetic analyses, the isolate is considered to represent a novel species, for which the name Geoglobus acetivorans sp. nov. is proposed. The type strain is SBH6(T) (=DSM 21716(T) =VKM B-2522(T)).

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A thermophilic, anaerobic, chemolithoautotrophic bacterium (designated strain SL50(T)) was isolated from a hydrothermal sample collected at the Mid-Atlantic Ridge from the deepest of the known World ocean hydrothermal fields, Ashadze field (1 degrees 58' 21'' N 4 degrees 51' 47'' W) at a depth of 4100 m. Cells of strain SL50(T) were motile, straight to bent rods with one polar flagellum, 0.5-0.6 mum in width and 3.0-3.5 mum in length. The temperature range for growth was 25-75 degrees C, with an optimum at 60 degrees C. The pH range for growth was 5.0-7.5, with an optimum at pH 6.5. Growth of strain SL50(T) was observed at NaCl concentrations ranging from 1.0 to 6.0 % (w/v) with an optimum at 2.5 % (w/v). The generation time under optimal growth conditions for strain SL50(T) was 60 min. Strain SL50(T) used molecular hydrogen, acetate, lactate, succinate, pyruvate and complex proteinaceous compounds as electron donors, and Fe(III), Mn(IV), nitrate or elemental sulfur as electron acceptors. The G+C content of the DNA of strain SL50(T) was 28.7 mol%. 16S rRNA gene sequence analysis revealed that the closest relative of strain SL50(T) was Deferribacter abyssi JR(T) (95.5 % similarity). On the basis of its physiological properties and phylogenetic analyses, the isolate is considered to represent a novel species, for which the name Deferribacter autotrophicus sp. nov. is proposed. The type strain is SL50(T) (=DSM 21529(T)=VKPM B-10097(T)). Deferribacter autotrophicus sp. nov. is the first described deep-sea bacterium capable of chemolithoautotrophic growth using molecular hydrogen as an electron donor and ferric iron as electron acceptor and CO(2) as the carbon source.

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A moderately thermophilic, anaerobic bacterium (strain SG 508T) was isolated from a hydrothermal vent chimney located at 1 degrees N on the East Pacific Rise at a depth of 2650 m. Cells of strain SG 508T were straight to slightly curved rods, 0.4-0.6 microm in diameter and 2.0-3.0 microm in length. Spore formation was observed only below pH 5.5. The temperature range for growth was 22-60 degrees C, with optimum growth at 50 degrees C. The pH range for growth was 4.0-8.5, with optimum growth at pH 6.0-6.8. Growth of strain SG 508T was observed at NaCl concentrations ranging from 1.0 to 6.0 % (w/v), with optimum growth at 2.5 % (w/v). Substrates utilized by strain SG 508T included casein, peptone, tryptone, yeast extract, beef extract, starch, maltose and glucose. The products of glucose fermentation were ethanol, acetate, H2, formate and CO2. Strain SG 508T was able to reduce elemental sulfur to hydrogen sulfide. The DNA G+C content of strain SG 508T was 30.9 mol%. 16S rRNA gene sequence analysis revealed that the isolated organism belonged to cluster I of the genus Clostridium. On the basis of its physiological properties and data from phylogenetic analyses, strain SG 508T is considered to represent a novel species of the genus Clostridium, for which the name Clostridium tepidiprofundi sp. nov. is proposed. The type strain is SG 508T (=DSM 19306T =VKM B-2459T).

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A moderately thermophilic, facultatively anaerobic bacterium capable of reducing Cr(VI) (strain SKC1) was isolated from municipal sewage. Based on the analysis of the 16S rRNA gene nucleotide sequence and DNA-DNA hybridization data, strain SKC1 was identified as a representative of the species Bacillus thermoamylovorans. B. thermoamylovorans SKC1 is capable of reducing chromate with L-arabinose as an electron donor with an optimum at 50 degrees C and neutral pH. The culture is able to reduce Cr(VI) at its initial concentration in the medium of up to 150 mg/l. In addition to chromate, strain SKC1 is capable of reducing selenite and tellurite, as well as soluble forms of Fe(III). It was shown that Cr(VI), Te(IV), and Se(IV) exert a bacteriostatic effect on strain SKC1, and the reduction of these anions performs the detoxification function. This is the first communication on the reduction of chromate, selenite, tellurite, and soluble Fe(III) species by a culture of thermophilic bacilli.

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A stable association of hyperthermophilic microorganisms (82 degrees C), which contained mostly cocci and a minor amount of non-spore-forming rods, was obtained from the fermented sludge of a methane tank used to process municipal wastewaters under thermophilic conditions (50 degrees C). PCR amplification of 16S rRNA genes using total DNA isolated from this association and archaea-specific primers, followed by sequencing of the product obtained, showed that the archaeal component was represented by a single nucleotide sequence, which was 99.9% homologous to 16S rRNA gene of Sulfophobococcus zilligii. Thus, a hyperthermophilic archaeon was for the first time detected in a system of anaerobic biological treatment of wastewater. In addition, this is the first report on the detection of a cultivated member of Crenarchaeota in anthropogenic habitats with neutral pH.

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