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

A moderately thermophilic, anaerobic bacterium (strain SG 508T) was isolated from a hydrothermal vent chimney located at 1 degrees N on the East Pacific Rise at a depth of 2650 m. Cells of strain SG 508T were straight to slightly curved rods, 0.4-0.6 microm in diameter and 2.0-3.0 microm 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 508T 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 508T included casein, peptone, tryptone, yeast extract, beef extract, starch, maltose and glucose. The products of glucose fermentation were ethanol, acetate, H2, formate and CO2. Strain SG 508T was able to reduce elemental sulfur to hydrogen sulfide. The DNA G+C content of strain SG 508T 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 508T 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 508T (=DSM 19306T =VKM B-2459T).