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)).