Physiological and phylogenetic diversity of thermophilic spore-forming hydrocarbon-oxidizing bacteria from oil fields

The distribution and population density of aerobic hydrocarbon-oxidizing ba cteria in the high-temperature oil fields of Western Siberia, Kazakhstan, a nd China were studied. Seven strains of aerobic thermophilic spore-forming bacteria were isolated from the oil fields and studied by microbiological a nd molecular biological methods. Based on the 16S rRNA gene sequences, phen otypic characteristics, and the results of DNA-DNA hybridization, the taxon omic affiliation of the isolates was tentatively established. The strains w ere assigned to the first and fifth subgroups of the genus Bacillus on the phylogenetic branch of the gram-positive bacteria. Strains B and 421 were c lassified as B. licheniformis. Strains X and U, located between B, stearoth ermophilus and B. thermocatenulatus on the phylogenetic tree, and strains K , Sam, and 34, related but not identical to B. themtodenitrificans and B. t hermoleovorans, undoubtedly represent two new species. Phylogenetically and metabolically related representatives of thermophilic bacilli were found t o occur in geographically distant oil fields.