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

Abstract
A novel mesophilic, hydrogen-oxidizing, sulfur-reducing bacterium, designated strain BKB25Ts-YT, was isolated from hydrothermal sediments at Iheya North in the Mid-Okinawa Trough, Japan. Cells were Gram-negative, motile rods (1·8–2·1 μm long and 0·5–0·7 μm 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 °C (optimum 32 °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 S0reduction with H2. 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 uncultivatedε-ProteobacteriaGroup G. On the basis of the physiological and molecular properties of the novel isolate, the genus nameThioreductorgen. nov. is proposed, withThioreductor micantisolisp. nov. as the type species. The type strain is BKB25Ts-YT(=JCM 12457T=DSM 16661T).