Thioreductor micantisoli gen. nov., sp. nov., a novel mesophilic, sulfur-reducing chemolithoautotroph within the epsilon-Proteobacteria isolated from hydrothermal sediments in the Mid-Okinawa Trough.

A novel mesophilic, hydrogen-oxidizing, sulfur-reducing bacterium, designated strain BKB25Ts-Y(T), was isolated from hydrothermal sediments at Iheya North in the Mid-Okinawa Trough, Japan. Cells were Gram-negative, motile rods (1.8-2.1 microm long and 0.5-0.7 microm wide). The isolate was a strictly anaerobic chemolithoautotroph capable of using molecular hydrogen as the sole energy source and carbon dioxide as the sole carbon source. Elemental sulfur and nitrate served as electron acceptors, respectively yielding hydrogen sulfide and ammonium. Growth was observed at 20-42 degrees C (optimum 32 degrees C; 3 h doubling time), pH 5.0-6.5 (optimum 6.0) and in the presence of 2.0-4.0 % NaCl (optimum 2.5 %) via respiratory S(0) reduction with H(2). The G+C content of the genomic DNA was 37.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate represented the first strain for which taxonomic properties have been characterized within the previously uncultivated epsilon-Proteobacteria Group G. On the basis of the physiological and molecular properties of the novel isolate, the genus name Thioreductor gen. nov. is proposed, with Thioreductor micantisoli sp. nov. as the type species. The type strain is BKB25Ts-Y(T) (=JCM 12457(T)=DSM 16661(T)).