Balnearium lithotrophicum gen. nov., sp nov., a novel thermophilic, strictly anaerobic, hydrogen-oxidizing chemolithoautotroph isolated from a black smoker chimney in the Suiyo Seamount hydrothermal system

A novel, extremely thermophilic bacterium, designated strain 17S(T), was isolated from a deep-sea hydrothermal vent chimney at the Suiyo Seamount in the Izu-Bonin Arc, Japan. The cells were rods with no apparent motility, most of which were narrow in the middle in the exponential-growth phase and had several polar flagella at both ends. Growth was observed between 45 and 80 degreesC (optimum temperature, 70-75 degreesC; doubling time, 80 min) and between pH 5.0 and 7.0 (optimum pH, 5.4). The isolate was a strictly anaerobic chemolithoautotroph that was capable of using molecular hydrogen as its sole energy source and carbon dioxide as its sole carbon source. Elemental sulfur (SO) was required for growth as an electron acceptor. The G+C content of the genomic DNA was 34.6 mol%. Phylogenetic analysis based on 16S rDNA sequences indicated that the isolate was related to Thermovibrio ruber ED11/3LLK(T) and Desulfurobacterium thermolithotrophum BSA(T), whilst it appeared to be a novel lineage prior to the divergence of these genera. This isolate could also be differentiated from both T ruber ED11/3LLK(T) and D. thermolithotrophum BSAT on the basis of physiological properties. The name Balnearium lithotrophicum gen. nov., sp. nov. is proposed for this isolate (type strain, 17 S-T=JCM 11970(T) =ATCC BAA-736(T)).