Microbial characterization of a JP-4 fuel-contaminated site using a combined lipid biomarker/polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)-based approach

The impact of pollution on soil microbial communities and subsequent biorem ediation can be measured quantitatively in situ using direct, non-culture-d ependent techniques. Such techniques have advantages over culture-based met hods, which often account for less than 1% of the extant microbial communit y. In 1988, a JP-4 fuel spill contaminated the glacio-fluvial aquifer at Wu rtsmith Air Force Base, Michigan, USA. In this study, lipid biomarker chara cterization of the bacterial and eukaryotic communities was combined with p olymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of the eubacterial community to evaluate correlation between cont aminant (JP-4 fuel) concentration and community structure shifts. Vadose, c apillary fringe and saturated zone samples were taken from cores within and up- and down-gradient from the contaminant plume, Lipid biomarker analysis indicated that samples from within the plume contained increased biomass, with large proportions of typically Gram-negative bacteria. Outside the plu me, lipid profiles indicated low-biomass microbial communities compared wit h those within the initial spill site. 16S rDNA sequences derived from DGGE profiles from within the initial spill site suggested dominance of the eub acterial community by a limited number of phylogenetically diverse organism s. Used in tandem with pollutant quantification, these molecular techniques should facilitate significant improvements over current assessment procedu res for the determination of remediation end-points.