Impact of microbial community structure on crude oil biodegradation

Crude oil-degrading enrichment cultures were developed to investigate the impact of microbial community structure in crude oil biodegradation. Analysis of the biodegradation products of five cultures enriched from hydrocarbon impacted soils revealed extensive degradation of the saturate fraction, including recalcitrant compounds such as hopanes. Microbial analysis using denaturing gradient gel electrophoresis (DGGE) revealed differences between the communities in the five enrichment cultures, suggesting that the ability to degrade hopanes may be common to several different microorganisms.; In order to investigate the role of the n-alkanes and n-alkane-degrading organisms on microbial community structure, two cultures (enrichments A and B) were enriched simultaneously in the presence and absence of n-alkanes. Enrichment A, developed in the presence of n-alkanes, extensively degraded the saturate fraction of the oil (93%), but showed no degradation of aromatic compounds. Enrichment B, developed in the absence of n-alkanes, degraded 96% of the aromatic compounds monitored. Further analysis demonstrated that enrichment A did not degrade aromatics even in the absence of n-alkanes, while enrichment B degraded the n-alkanes. DGGE analysis of the microbial communities in these cultures revealed that although some similarities existed between the cultures, the microbial populations were significantly different and enrichment B was more diverse.; Growth on n-alkanes can be mediated by two principal uptake mechanisms, interfacial accession influenced by cell surface hydrophobicity, and enhanced solubilization, mediated by biosurfactant production. Isolates A1 and A3 were shown to produce biosurfactants, a quorum sensing regulated phenotype, and the distinct morphology of the isolates (A1 = smooth colonies and A3 = rough colonies) has been associated to hydrophobicity changes in clinical P. aeruginosa isolates. Results suggest that A1 and A3 uptake n-alkanes via interfacial accession and that the switch in morphology represents an adaptive response that increases cell surface hydrophobicity to enhance hydrophobic hydrocarbon uptake. This switch is indispensable for the utilization of n-alkanes in our system, which is required to attain the cell density threshold for AHL and biosurfactant production. Thus, cell surface hydrophobicity and quorum-sensing regulated biosurfactant production represent potential avenues for the manipulation of n-alkane-degrading populations. (Abstract shortened by UMI.)...