Desulfurobacterium thermolithotrophum gen. nov., sp. nov., a novel autotrophic, sulphur-reducing bacterium isolated from a deep-sea hydrothermal vent

A thermophilic, anaerobic, strictly autotrophic, sulphur-reducing bacterium, designated BSAT(T = type strain), was isolated from a deep-sea hydrothermal chimney sample collected at the mid-Atlantic ridge. Gram-negative cells occurred singly or in pairs as small highly motile rods. Spores were not observed. The temperature range for growth was 40 to 75°C, with an optimum at 70 °C. The pH range for growth at 70 °C was from 4·4 to 7·5, with an optimum around 6·0. The sea salt concentration range for growth was 15–70 g I-1with an optimum at 35 g I-1. Elemental sulphur, thiosulphate and sulphite were reduced to hydrogen sulphide. Sulphate and cystine were not reduced. The G+C content of the genomic DNA was 35 mol%. Phylogenetic analyses of the 16S rRNA gene indicated that the strain was a member of the domain Bacteria and formed a branch that was almost equidistant from members of the orders Aquificales and Thermotogales. The new organism possesses phenotypic and phylogenetic traits that do not allow its classification as a member of any previously described genus; therefore, it is proposed that this isolate should be described as a member of a novel species of a new genus, Desulfurobacterium gen. nov., of which Desulfurobacterium thermolithotrophum sp. nov. is the type species. The type strain is BSAT(= DSM 11699T).