Exploring the role of Pseudomonas aeruginosa in crude oil biodegradation

In this study, we examined the ability of Pseudomonas aeruginosa to alter the functional diversity of a crude oil-degrading microbial community. When grown on crude oil, P. aeruginosa was first observed to rapidly adapt to growth on the hydrophobic substrate by decreasing the expression of highly charged B-band lipopolysaccharide molecules on its cell surface. This adaptation increased cell surface hydrophobicity and resulted in enhanced attachment to and utilization of crude oil components by P. aeruginosa. The rapid adaptation to growth on crude oil resulted in increased cell density and the subsequent production of micromolar concentrations of the antibacterial compound, pyocyanin. This compound was further demonstrated to inhibit members of the crude oil-degrading community expressing low levels of the antioxidant enzymes superoxide dismutase and catalase. The pyocyanin-induced decrease in microbial diversity resulted in decreased overall degradation of PAHs and complex saturates by the community. Furthermore, a null mutation in the rhlI gene of the rhlIR quorum sensing pathway decreased pyocyanin production by P. aeruginosa isolates. When added to crude oil degrading communities, these mutants did not affect microbial diversity and resulted in enhanced oil degradation. Lastly, we examined the effect of adding a quorum sensing inhibitor, brominated furanones, to a crude oil degrading culture containing wild-type P. aeruginosa. The addition of 75 muM of a synthesized brominated furanone mixture to the cultures decreased pyocyanin production by P. aeruginosa and resulted in overall enhanced crude oil degradation by the community. These data indicate that inhibiting P. aeruginosa quorum sensing can reduce its competitiveness within a crude oil-degrading community resulting in enhanced oil degradation.