DESULFUROBACTERIUM THERMOLITHOTROPHUM GEN. NOV., SP. NOV., A NOVEL AUTOTROPHIC, SULFUR-REDUCING BACTERIUM ISOLATED FROM A DEEP-SEA HYDROTHERMAL VENT

A thermophilic, anaerobic, strictly autotrophic, sulphur-reducing bact erium, designated BSA(T) (T = type strain), was isolated from a deep-s ea hydrothermal chimney sample collected at the mid-Atlantic ridge. Gr am-negative cells occurred singly or in pairs as small highly motile r ods. Spores were not observed. The temperature range for growth was 40 to 75 degrees C, with an optimum at 70 degrees C, The ph range for gr owth at 70 degrees 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 l(-1) with an optimum at 35 g l(-1). Elemental sulphur, thiosulphate and sulphite we re reduced to hydrogen sulphide. Sulphate and cystine were not reduced . The G+C content of the genomic DMA was 35 mol%. Phylogenetic analyse s of the 16S rRNA gene indicated that the strain was a member of the d omain Bacteria and formed a branch that was almost equidistant from me mbers of the orders Aquificales and Thermotogales, The new organism po ssesses phenotypic and phylogenetic traits that do not allow its class ification as a member of any previously described genus; therefore, it is proposed that this isolate should be described as a member of a no vel species of a new genus, Desulfurobacterium gen. nov., of which Des ulfurobacterium thermolithotrophum sp. nov, is the type species. The t ype strain is BSA(T) (= DSM 11699(T)).