Identification of distinct communities of sulfate-reducing bacteria in oil fields by reverse sample genome probing

Thirty-five different standards of sulfate-reducing bacteria, identified by reverse sample genome probing and defined as bacteria with genomes showing little or no cross-hybridization, were in part characterized by Southern blotting, using 16S rRNA and hydrogenase gene probes. Samples from 56 sites in seven different western Canadian oil field locations were collected and enriched for sulfate-reducing bacteria by using different liquid media containing one of the following carbon sources: lactate, ethanol, benzoate, decanoate, propionate, or acetate. DNA was isolated from the enrichments and probed by reverse sample genome probing using master filters containing denatured chromosomal DNAs from the 35 sulfate-reducing bacterial standards. Statistical analysis of the microbial compositions at 44 of the 56 sites indicated the presence of two distinct communities of sulfate-reducing bacteria. The discriminating factor between the two communities was the salt concentration of the production waters, which were either fresh water or saline. Of 34 standards detected, 10 were unique to the fresh water and 18 were unique to the saline oil field environment, while only 6 organisms were cultured from both communities.