Tepidibaculum saccharolyticum gen. nov., sp. nov. a moderately thermophilic, anaerobic, spore-forming bacterium isolated from a terrestrial hot spring.

A novel moderately thermophilic, anaerobic bacterium, strain STR9 was isolated from terrestrial hot spring at Uzon Caldera, Kamchatka peninsula, Russia. Cells of strain STR9 were spore-forming motile straight or slightly curved rods 0.3 μm in diameter and 1.0-2.0 μm in length having a Gram-positive cell-wall structure. The temperature range for growth was 30-58 °C, with an optimum at 50 °C. The pH range for growth was 5.0-10.5, with an optimum at pH 8.0-9.0. NaCl inhibited growth of the strain STR9 and no growth was evident above 0.5% NaCl (w/v). Several mono-, di-, and polysaccharides as well as beef extract and yeast extract supported growth. The main end products of glucose fermentation were ethanol, acetate, hydrogen, and carbon dioxide. The G + C content of DNA of strain STR9 was 40.0 mol% (T). Analysis of the 16S rRNA gene sequences revealed that strain STR9 belongs to the family Ruminococcaceae, class Clostridia, with less than 93% 16S rRNA gene sequence similarity to any species with validly published name. We propose to assign strain STR9 to a new species of a novel genus Tepidibaculum saccharolyticum gen. nov., sp. nov. The type strain is STR9 (= DSM 28577 = VKM B-2882 = UNIQEM STR9).