My Research

I am studying the effects of redox conditions on bacterial communities in mercury-contaminated soil. For a more technical explanation, check out my abstract for the Symposium on Undergraduate Research Experience (SURE) Conference.

Mercury is a pretty nasty neurotoxin in any form, but methylmercury is the worst because it bioaccumulates in muscle and livers and can biomagnify through the food chain. Thus, species that are higher up in the food chain, like large predators and humans, are exposed to dangerously high levels of methylmercury.

Methylmercury is of concern in the Adirondacks for two major reasons: its levels are dangerously high, and there are few local sources of contamination – mercury in the Adirondacks comes primarily from surrounding states and even as far as China via atmospheric deposition. We've chosen to focus on two areas, Huntington Forest and Sunday Lake, because they represent both wetland and forest vegetation.

Very little is known about methylation, the process by which bacteria transform ionic mercury to methylmercury. Sulfate-reducing bacteria have been identified as methylators, but other species of bacteria may methylate as well. By placing soil under different redox conditions, I can assess which species of bacteria are involved in mercury cycling.

Jon Schwenk, a fellow REU student, created artificial redox conditions by generating soil columns. As the conditions changed in the columns, the bacterial community structure changed (some bacteria cannot survive in specific conditions, while others may thrive). I'm attempting to analyze the bacterial community for soil under different conditions.

After Jon ran his soil columns, I extracted DNA from the soil, amplified (ie, made more of it) it using Polymerase Chain Reaction (PCR), and separated the species using Denaturing Gradient Gel Electrophoresis (DGGE). In the future, I will be able to determine the bacterial community size and structure by analyzing my DGGE results and sending DNA to a lab for sequencing.

By comparing changes in bacterial communities with methylmercury flux in the soil columns, I should be able to draw conclusions about which bacterial species are involved in methylation. This could ultimately lead to management solutions that could reduce methylmercury production.

I plan to continue investigating this topic throughout my senior year at Clarkson.