Taxonomic study of aerobic thermophilic bacilli: descriptions of Geobacillus subterraneus gen. nov., sp nov and Geobacillus uzenensis sp nov from petroleum reservoirs and transfer of Bacillus stearothermophilus Bacillus thermocatenulatus, Bacillus thermoleovorans, Bacillus kaustophilus, Bacillus thermoglucosidasius and Bacillus thermodenitrificans to Geobacillus as the new combinations G-stearothermophilus, G-thermocatenulatus, G-thermoleovorans, G-kaustophilus, G-thermoglucosidasius and G-therm

Five hydrocarbon-oxidizing strains were isolated from formation waters of o ilfields in Russia, Karakhstan and China. These strains were moderately the rmophilic, neutrophilic, motile, spore-forming rods, aerobic or facultative ly anaerobic. The G+C content of their DNA ranged from 49.7 to 52.3 mol%. T he major isoprenoid quinone was menaquinone-7; cellular fatty acid profiles consisted of significant amounts of iso-15:0, iso-16:0 and iso-17:0 fatty acids (61.7-86.8% of the total). Based on data from 16S rDNA analysis and D NA-DNA hybridization, the subsurface isolates could be divided into two gro ups, one of which consisted of strains U-T and X and the other of which con sisted of strains K, Sam and 34(T). The new strains exhibited a close phylo genetic relationship to thermophilic bacilli of 'Group 5' of Ash et al. [As h, C., Farrow, J. A. E., Wallbanks, S. & Collins, M. D. (1991). Left Appl M icrobiol 13, 202-206] and a set of corresponding signature positions of 16S rRNA. Comparative analysis of the 16S rDNA sequences and fatty acid compos itions of the novel isolates and established species of thermophilic bacill i indicated that the subsurface strains represent two new species within a new genus, for which the names Geobacillus subterraneus gen, nov., sp. nov. , and Geobacillus uzenensis sp, nov. are proposed. It is also proposed that Bacillus stearothermophilus, Bacillus thermoleovorans, Bacillus thermocate nulatus, Bacillus kaustophilus, Bacillus thermoglucosidasius and Bacillus t hermodenitrificans be transferred to this new genus, with Geobacillus stear othermophilus (formerly Bacillus stearothermophilus) as the type species.