Bacterial community changes in diesel-oil-contaminated soil microcosms biostimulated with Luria-Bertani medium or bioaugmented with a petroleum-degrading bacterium, Pseudomonas aeruginosa strain WatG.

The microbial community structure of diesel-oil-contaminated soil microcosms biostimulated with Luria-Bertani medium (LB-BS) or bioaugmented with a petroleum-degrading bacterium, Pseudomonas aeruginosa strain WatG (WatG-BA), was investigated by denaturing gradient gel electrophoresis (DGGE) and by monitoring diesel oil degradation. The degradation in WatG-BA (64.0% +/- 4.2%) was higher than that in LB-BS (49.5% +/- 12.0%) during the first two weeks. The microbial community in WatG-BA, which was markedly dominated by strain WatG, was much simpler than that in LB-BS, where hydrocarbon degraders occurred after a lag of 3-7 days after the addition of diesel oil. The clustering profiles of the DGGE banding patterns of the two soil microcosms were only 12% similar. This difference is probably due to antibacterial substances, such as rhamnolipids, secreted by strain WatG.