Oceanithermus desulfurans sp. nov., a novel thermophilic, sulfur-reducing bacterium isolated from a sulfide chimney in Suiyo Seamount

A novel thermophilic, microaerophilic, sulfur-reducing bacterium designated strain St55B^T was isolated from a sulfide chimney in the hydrothermal field of Suiyo Seamount (Izu-Bonin Arc, Western Pacific). Cells of the isolate were rod-shaped and tended to form a chain-link circular structure (a rotund body) at exponential phase under good growth conditions. The isolate was a chemoheterotroph requiring yeast extract for growth. Although strain St55B^T used oxygen as an electron acceptor, it could not form colonies in an oxygen concentration of more than 5% (v/v). The isolate also used nitrate, nitrite or elemental sulfur in the absence of oxygen. A phylogenetic analysis based on the 16S RNA gene sequence revealed that the isolate was closely related to Oceanithermus profundus, belonging to the phylum 'Deinococcus-Thermus' (sequence similarity 99.5%). However, strain St55B^T differed from O. profundus in terms of usage of electron donors, cellular fatty acid profile and DNA G + C content. In addition, a DNA-DNA hybridization test indicated low relatedness between the isolate and O. profundus. For the reasons given above, the name Oceanithermus desulfurans sp. nov. is proposed for strain St55B^T (= NBRC 100063^T =DSM 15757^T).