Desulfomarina profundi gen. nov., sp. nov., a novel mesophilic, hydrogen-oxidizing, sulphate-reducing chemolithoautotroph isolated from a deep-sea hydrothermal vent chimney.

A novel mesophilic, strictly anaerobic, chemolithoautotrophic sulphate-reducing bacterium, designated strain KT2 ^T , was isolated from a deep-sea hydrothermal vent chimney at the Suiyo Seamount in the Izu-Bonin Arc. Strain KT2 ^T grew at 25-40 °C (optimum 35 °C) and pH 5.5-7.0 (optimum 6.6) in the presence of 25-45 g l ^-1 NaCl (optimum 30 g l ^-1 ). Growth occurred with molecular hydrogen as the electron donor and sulphate, thiosulphate, and sulphite as the electron acceptors. The isolate utilized CO ₂ as the sole carbon source for chemolithoautotrophic growth on H ₂ . Glycerol, succinate, fumarate, malate, glutamate, or casamino acids could serve as an alternative electron donor in the presence of CO ₂ . Malate, citrate, glutamate, and casamino acids were used as fermentative substrates for weak growth. The G+C content of genomic DNA was 46.1 %. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain KT2 ^T is a member of the family Desulfobulbaceae , showing a sequence similarity of 94.3 % with Desulforhopalus singaporensis . Phylogenomic analysis based on concatenated 156 single-copy marker genes confirmed the same topology as the 16S rRNA gene phylogeny. The ANI and AAI values between strain KT2 ^T and related genera of the family Desulfobulbaceae were 65.6-68.6 % and 53.1-62.9 %. Based on the genomic, molecular, and physiological characteristics, strain KT2 ^T represents a novel genus and species within the family Desulfobulbaceae , for which the name Desulfomarina profundi gen. nov., sp. nov. is proposed, with KT2 ^T (=JCM 34118 ^T = DSM 111364 ^T ) as the type strain.