Thermoanaerobacter subterraneus sp. nov., a novel thermophile isolated from oilfield water.

A new thermophilic, anaerobic glucose-fermenting, Gram-positive, rod-shaped bacterium, designated strain SEBR 7858T, was isolated from an oilfield water sample. Under optimal conditions on a glucose-containing medium (3% NaCl, 65 degrees C and pH 7.5), the generation time was 2.5 h. No growth occurred at 35 or 80 degrees C, nor at pH 5..5 or 9.0. Strain SEBR 7858T possessed lateral flagella. Spores were undetected but heat-resistant forms were present. Strain SEBR 7858T fermented a range of carbohydrates to acetate, L-alanine, lactate, H2 and CO2. The isolate reduced thiosulfate and elemental sulfur, but not sulfate or sulfite to sulfide. In the presence of thiosulfate, the ratio of acetate produced per mole of glucose consumed increased, suggesting a shift in the use of electron acceptors during carbohydrate metabolism. The DNA G+C content was 41 mol%. Based on 16S rRNA gene sequence analysis, the strain was almost equidistantly related to all members of the genus Thermoanaerobacter (mean similarity 92%). Based on phenotypic, genomic and phylogenetic characteristics, strain SEBR 7858T was clearly different from all members of the genus Thermoanaerobacter and was therefore designated as a new species, Thermoanaerobacter subterraneus sp. nov. The type strain is SEBR 7858T (= CNCM 1-2383T, DSM 13054T).