Desulfothermobacter acidiphilus gen. nov., sp nov., a thermoacidophilic sulfate-reducing bacterium isolated from a terrestrial hot spring

An anaerobic sulfate-reducing micro-organism, strain 3408-1(T), was isolated from a terrestrial hot spring in Kamchatka peninsula (Russia). The cells were spore-forming rods with a Gram-positive type of cell wall. The new isolate was a moderately thermoacidophilic anaerobe able to grow either by sulfate or thiosulfate respiration with H-2 or formate as substrates, or by fermenting yeast extract, maltose, sucrose, glucose and pyruvate. The fermentation products were acetate, CO2 and H-2. The pH range for growth was 2.9-6.5, with an optimum at 4.5. The temperature range for growth was 42-70 degrees C, with an optimum at 55 degrees C. The G+C content of DNA was 58 mol%. Phylogenetic analysis of the 16S rRNA gene showed that strain 3408-1(T) belongs to the family Thermoanaerobacteraceae, order Thermoanaerobacterales and was distantly related to the species of the genus Ammonifex (93-94 % sequence similarity). On the basis of physiological properties and results of phylogenetic analysis, strain 3408-1(T) is considered to represent a novel species of a new genus, for which the name Desulfothermobacter acidiphilus gen. nov., sp. nov. is proposed. The type strain is 3408-1(T) (=DSM 105356(T) =VKM B-3183(T)).