Molecular- and cultural-based monitoring of bioremediation at a TCE-contaminated site

Sediment samples from a trichloroethylene (TCE)-contaminated zone 30 to 47 m below ground surface were analyzed after various nutrient addition strategies, including injection of air, 1% methane (in air), 4% methane (in air) pulsed with air, and multiple nutrients. Methanotroph most probable number (MPN) values in samples taken after the N/P/pulsed 4% methane campaign increased approximately two orders of magnitude compared to before-methane samples. The frequency of TCE biodegradative potential in methanotroph enrichments from samples taken after the N/P/pulsed 4% methane campaign was orders of magnitude greater than in all previous campaigns, indicating that in situ microbial activity was very strongly affected by adding nitrogen and phosphorus. The frequency of detection of the soluble methane monooxygenase and methanol dehydrogenase sequences was highest in sediment samples taken after the 1% methane campaign. Comparing the culture-dependent method with the culture-independent gene probe method showed that the culture method greatly underestimated the methanotrophic biomass in sediments throughout the demonstration.