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...

Three strains of facultatively aerobic, moderately thermophilic bacteria were isolated from terrestrial hot springs in Baikal Lake region and Kamchatka (Russia). Cells of the new isolates were cocci reproducing by binary fission. The temperature range for growth was between 20 and 56 6C and the pH range for growth from pH 4.5 to 8.5, with optimal growth at 47-50 6C and pH 7.0-7.5. The organisms were chemoheterotrophs preferring sugars and polysaccharides as growth substrates. 16S rRNA gene sequences of strains 2842, 2813 and 2918Kr were nearly identical (99.7-100 % similarity) and indicated that the strains belonged to the phylum Planctomycetes. The phylogenetically closest cultivated relatives were Algisphaera agarilytica 06SJR6-2 T and Phycisphaera mikurensis FYK2301M01 T with 16S rRNA gene sequence similarity values of 82.4 and 80.3 %, respectively. The novel strains differed from them by higher growth temperature, sensitivity to NaCl concentration above 3.0 % and by their cellular fatty acids profile. On the basis of phylogenetic and physiological data, strains 2842 T , 2813 and 2918Kr represent a novel genus and species for which we propose the name Tepidisphaera mucosa sp. nov. The type strain is 2842 T (5VKM B-2832. We also propose that Tepidisphaera gen. nov. is the type genus of a novel family, Tepidisphaeraceae fam. nov. and a novel order, Tepidisphaerales ord. nov.Thermophilic micro-organisms represent diverse phylogenetic lineages of prokaryotes, including new deep ones (Cole et al., 2013; Kawaichi et al., 2013;Podosokorskaya et al., 2013). Some phylogenetic groups inhabiting thermal environments contain only thermophiles, while others contain organisms with different temperature characteristics (Lebedinsky et al., 2007). Thermophilic representatives are now found even in bacterial phyla previously considered to contain only mesophilic prokaryotes, such as the phylum Acidobacteria (Losey et al., 2013). Another example is the phylum Planctomycetes. Analysis of the diversity and distribution of this group in thermal environments based on environmental molecular data revealed several phylogenetic groups of the phylum Planctomycetes most frequently detected in these habitats (A. Yu. Merkel and others, unpublished results). Several isolates from different terrestrial and subsurface thermal habitats were obtained, enriched and/or isolated in pure cultures and identified as members of the new genus 'Thermogutta' (Slobodkina et al., 2014) which is part of the Pirellula-Blastopirellula-Rhodopirellula cluster. These organisms, together with a representative of the genus 'Thermopirellula' (name not validly published; Liu et al., 2012), are to our knowledge the first thermophilic representatives of the phylum Planctomycetes.Abbreviation: ECL, equivalent chain length.

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