Tepidibacter mesophilus sp. nov., a mesophilic fermentative anaerobe isolated from soil polluted by crude oil, and emended description of the genus Tepidibacter.

A mesophilic, aerotolerant, endospore-forming, fermentative bacterium, designated strain B1(T), was isolated from soil polluted by crude oil in the Karamay Oil Field, China. Cells were Gram-positive, rod-shaped, 1.1-1.6 µm wide and 2.3-4.7 µm long, and were motile by means of peritrichous flagella. Growth occurred at 10-40 °C and pH 6.0-8.9; optimal growth occurred at 28-32 °C and pH 7.3. The optimal concentrations of NaCl and sea salts for growth were 0.5 and 1% (w/v), respectively. The strain was halotolerant and grew in the presence of NaCl or sea salts up to a concentration of 9% (w/v). Substrates utilized as sole carbon sources were beef extract, yeast extract, peptone, tryptone, casein, D-glucose, D-fructose, D-xylose, D-ribose, D-galactose, maltose, L-rhamnose, trehalose, L-valine, DL-alanine plus L-proline and DL-alanine plus L-glycine. The main products of glucose fermentation were ethanol and acetate. iso-C(15:0), iso-C(14:0), C(16:0) and iso-C(13:0) were the major fatty acids. 16S rRNA gene sequence analysis revealed that the isolate belongs to the genus Tepidibacter, showing 94.7 and 94.1% similarity to the type strains of Tepidibacter formicigenes and Tepidibacter thalassicus, respectively. The genomic DNA G+C content of strain B1(T) was 29.8 mol%. On the basis of its phenotypic and genotypic properties, strain B1(T) is suggested to represent a novel species of the genus Tepidibacter, for which the name Tepidibacter mesophilus sp. nov. is proposed. The type strain is B1(T) (=CGMCC 1.5148(T) =JCM 16806(T)).