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, 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 H2 or formate as substrates, or by fermenting yeast extract, maltose, sucrose, glucose and pyruvate. The fermentation products were acetate, CO2 and H2. The pH range for growth was 2.9-6.5, with an optimum at 4.5. The temperature range for growth was 42-70 °C, with an optimum at 55 °C. The G+C content of DNA was 58 mol%. Phylogenetic analysis of the 16S rRNA gene showed that strain 3408-1 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 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 (=DSM 105356=VKM B-3183).