Clostridium tepidiprofundi sp nov., a moderately thermophilic bacterium from a deep-sea hydrothermal vent

A moderately thermophilic, anaerobic bacterium (strain SG 508(T)) was isolated from a hydrothermal vent chimney located at 13 degrees N on the East Pacific Rise at a depth of 2650 m. Cells of strain SG 508(T) were straight to slightly curved rods, 0.4-0.6 mu m in diameter and 2.0-3.0 mu m in length. Spore formation was observed only below pH 5.5. The temperature range for growth was 22-60 degrees C, with optimum growth at 50 degrees C. The pH range for growth was 4.0-8.5, with optimum growth at pH 6.0-6.8. Growth of strain SG 508(T) was observed at NaCl concentrations ranging from 1.0 to 6.0 % (w/v), with optimum growth at 2.5 % (w/v). Substrates utilized by strain SG 508(T) included casein, peptone, tryptone, yeast extract, beef extract, starch, maltose and glucose. The products of glucose fermentation were ethanol, acetate, H-2, formate and CO2. Strain SG 508(T) was able to reduce elemental sulfur to hydrogen sulfide. The DNA G + C content of strain SG 508(T) was 30.9 mol%. 16S rRNA gene sequence analysis revealed that the isolated organism belonged to cluster I of the genus Clostridium. On the basis of its physiological properties and data from phylogenetic analyses, strain SG 508(T) is considered to represent a novel species of the genus Clostridium, for which the name Clostridium tepidiprofundi sp. nov. is proposed. The type strain is SG 508(T) (=DSM 19306(T) =VKM B-2459(T)).