Microbial Structure of

Coal-Tar Impacted Sites

Research Objective:

Fluorescence In-Situ Hybridizations (FISH) are being coupled with more traditional groundwater monitoring techniques to evaluate a coal-tar impacted aquifer in Northwestern Iowa for intrinsic bioremediation potential. FISH is a molecular method that allows semi-quantitative identification of specific microorganisms without cultivation. It is the process of binding (hybridizing) a small oligonucleotide probe containing a reporter molecule to complimentary cellular rRNA in target cells. rRNA is an ideal target because it contains both highly conserved and highly variable regions of genetic coding. When visualized under a microscope, microbes in complex environmental samples can be identified and enumerated. This lends to the ability to infer the occurrance of specific microbial processes based on differences in microbial structure associated with specific system perturbations. In the case of the coal-tar impacted aquifer. we are specifically looking for an increase of gross microbes associated with the contaminant plume, changes in groundwater redox chemistry that would be consistent to microbially-induced oxidation-reduction reactions, decreasing contaminant concentrations with time at individual sampling locations, and the enrichment in specific taxa that are known to harbor PAH-degrading microorganisms. We are probing the aquifer soils with oligos specific to the taxa shown in yellow. The stars denote taxa which harbor known PAH-degrading organisms, and are of particular interest.