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Thermosulfurimonas dismutans gen. nov., sp. nov., an extremely thermophilic sulfur-disproportionating bacterium from a deep-sea hydrothermal vent 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 mm in diameter and 1.0-1.5 mm in length, growing singly or in pairs. Cells were motile with a single polar flagellum. The temperature range for growth was 50-92 6C, with an optimum at 74 6C. 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 (5DSM 24515 T 5VKM B-2683 T ) is the type strain of the type species. This is the first description of a thermophilic microorganism that disproportionates elemental sulfur.Biogeochemical cycling of sulfur in aquatic environments includes the activities of different aerobic and anaerobic prokaryotes. Bacteria that disproportionate sulfur compounds such as thiosulfate or elemental sulfur (Bak & Cypionka, 1987;Thamdrup et al., 1993) are a unique group of sulfur cycle micro-organisms. Sulfur isotope data from early Archaean rocks and the presence of microfossils in 3.4-billion-year-old geological formations suggest that sulfur disproportionation could be one of the earliest modes of microbial metabolism (Philippot et al., 2007;Wacey et al., 2011). Inorganic sulfur fermentation has been reported for members of the mesophilic genera Desulfovibrio, Desulfobulbus, Desulfocapsa, Desulfonatronum, Desulfonatronospira and Desulfonatronovibrio in the Deltaproteobacteria (Bak & Pfennig, 1987;Lovley & Phillips, 1994;Janssen et al., 1996;Pikuta et al., 2003;Sorokin et al., 2008 Sorokin et al., , 2011. Among thermophiles, Desulfotomaculum thermobenzoicum is the only micro-organism that has been reported to be capable of growth by thiosulfate disproportionation (Jackson & McInerney, 2000). Prior to this report, no thermophiles were known to disproportionate elemental sulfur. S 0 is abundant in thermal ecosystems, including deep-sea hydrothermal vents, where it forms when hydrogen sulfide-rich hydrothermal fluid mixes w...

Microbial communities of Kamchatka Peninsula terrestrial hot springs were studied using molecular, radioisotopic and cultural approaches. Analysis of 16S rRNA gene fragments performed by means of high-throughput sequencing revealed that aerobic autotrophic sulfur-oxidizing bacteria of the genus Sulfurihydrogenibium (phylum Aquificae) dominated in a majority of streamers. Another widely distributed and abundant group was that of anaerobic bacteria of the genus Caldimicrobium (phylum Thermodesulfobacteria). Archaea of the genus Vulcanisaeta were abundant in a high-temperature, slightly acidic hot spring, where they were accompanied by numerous Nanoarchaeota, while the domination of uncultured Thermoplasmataceae A10 was characteristic for moderately thermophilic acidic habitats. The highest rates of inorganic carbon assimilation determined by the in situ incubation of samples in the presence of C-labeled bicarbonate were found in oxygen-dependent streamers; in two sediment samples taken from the hottest springs this process, though much weaker, was found to be not dependent on oxygen. The isolation of anaerobic lithoautotrophic prokaryotes from Kamchatka hot springs revealed a wide distribution of the ability for sulfur disproportionation, a new lithoautotrophic process capable to fuel autonomous anaerobic ecosystems.

Samples of water from the hot springs of Uzon Caldera with temperatures from 68 to 87°C and pHs of 4.1 to 7.0, supplemented with proteinaceous (albumin, casein, or ␣-or ␤-keratin) or carbohydrate (cellulose, carboxymethyl cellulose, chitin, or agarose) biological polymers, were filled with thermal water and incubated at the same sites, with the contents of the tubes freely accessible to the hydrothermal fluid. As a result, several enrichment cultures growing in situ on different polymeric substrates were obtained. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments obtained after PCR with Bacteria-specific primers showed that the bacterial communities developing on carbohydrates included the genera Caldicellulosiruptor and Dictyoglomus and that those developing on proteins contained members of the Thermotogales order. DGGE analysis performed after PCR with Archaea-and Crenarchaeota-specific primers showed that archaea related to uncultured environmental clones, particularly those of the Crenarchaeota phylum, were present in both carbohydrate-and protein-degrading communities. Five isolates obtained from in situ enrichments or corresponding natural samples of water and sediments represented the bacterial genera Dictyoglomus and Caldanaerobacter as well as new archaea of the Crenarchaeota phylum. Thus, in situ enrichment and consequent isolation showed the diversity of thermophilic prokaryotes competing for biopolymers in microbial communities of terrestrial hot springs.

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 (126 589 210 N 446 519 470 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 mm in diameter. The temperature range for growth was 50-85 6C, with an optimum at 81 6C. 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 (5DSM 21716 T 5VKM B-2522 T ).Iron minerals are abundant in deep-sea hydrothermal vents. The surfaces of active chimneys are frequently covered with deposits of iron oxides in different oxidative states, and the amount of iron in hydrothermal fluid can reach molar concentrations. Thus, deep-sea hydrothermal vents can provide an ecological niche for Fe(III)-reducing micro-organisms (Slobodkin et al., 2001). However, only a few thermophilic Fe(III)-reducers have been isolated from this environment. Currently, thermophilic and hyperthermophilic iron-reducing micro-organisms recovered from deep-sea habitats include two species of the Bacteria, Geothermobacter ehrlichii (Kashefi et al., 2003) and Deferribacter abyssi (Miroshnichenko et al., 2003), and three representatives of the Archaea, Thermococcus sp. SN531 (Slobodkin et al., 2001), Geoglobus ahangari (Kashefi et al., 2002) and 'Candidatus Aciduliprofundum boonei ' (Reysenbach et al., 2006). In this paper, we report the isolation and characterization of a novel hyperthermophilic Fe(III)-reducing archaeon from the deepest of the known World Ocean hydrothermal fields.Strain SBH6 T was isolated from a fragment of a hydrothermal chimney-like structure. The sample was collected in March 2007 during the Serpentine cruise at the Ashadze hydrothermal field (12 u 589 210 N 44 u 519 470 W) on the Mid-Atlantic Ridge at a depth of 4100 m. For sample collection, sterilized microbiological boxes filled with...