Sand Aggregation by Methanotrophic Bacteria and Marine Microbial Hydrocarbon Degradation Under Differing Biogeochemistries

Methanotrophic bacteria, bacteria that can metabolize methane, are ubiquitous, EPS-producing, and capable of degrading hundreds of contaminants (Hazen, 2010). This dissertation looks at the possibility of using methanotrophic bacteria in sand surface aggregation and oil spill responses. Sand aggregation practices are widely used from infrastructure improvements to reversing desertification. In chapter 2, two selected methanotrophic cultures had their growth curves measured and their extracellular polymeric substances (EPS) production estimated. This second chapter tested and rejected two null hypotheses; the first null hypothesis was that there is no difference in EPS production rates over a culture’s growth curve, showing that the exponential phase had the largest EPS production rates for both Methylocystis sp. and Methylosinus sporium. In chapter 3, two bench-scale experiments were set up to test the sand bioaggregation capabilities of methanotrophs. This third chapter had two null hypotheses, both of which were rejected, the first stating that there is no difference in aggregation between sand treated with different methanotrophic cultures, and the second null hypothesis is that there is no difference in aggregation based on when in their growth curve cultures are applied to sand. It was found that bacterial cultures applied during their stationary phase created the most stable aggregates as compared to those applied in their exponential phase. The fifth chapter aimed to determine how enriched microbial communities and their hydrocarbon degradation rates reacted to changes in biogeochemistry and methane amendments. There were three null hypotheses for the fifth chapter, all of which failed to be rejected, the last of which states that there is no difference in the methanotrophic percentage of the taxa plot with the addition of methane amendments. Overall, chapter 5 found that enriched microbial consortia had slightly better polyaromatic hydrocarbons (PAH) degradation in media that more closely mimicked their natural biogeochemistry and that the enriched consortia did not see an increase in hydrocarbon degradation.