Phone: 864 656-6915
Research in my lab is focused on environmental microbiology, specifically survival of stress. When we examine the world around us, it is possible to see microbial communities living in surprising places. While many of these microbial communities do not live in so-called extreme environments, they still must survive stressful conditions. These conditions include exposure to UV light, desiccation, and nutrient limitation. In many cases, microbes must not only survive these natural stresses, but also in the presence of manmade stressors in the form of xenobiotic compounds (pollutants) that we release into the environment. It is the mechanisms and strategies used by microbes to survive these conditions that my laboratory is interested in understanding. Our examination of these strategies uses several systems to ask the question: What are these microbes producing to survive these conditions and how do they use these materials to survive in these stressful environments?
Our first study system is from the deserts of southeast and south-central Utah. This microbial ecosystem resides in the surfaces of exposed sandstones and is technically a cryptoendolithic microbial community (living within the pores). We have determined that these communities stabilize the surfaces of these sandstones, which are highly erodible. Further work by my group is examining the role of extracellular materials with regard to the binding and stabilization of iron(II). Our hypothesis is that microbes and light reduce iron(III) to iron(II), making it mobile in the environment. The ferrous iron (iron(II)) is then bound by an extracellular polysaccharide (EPS) that binds and stabilizes it, preventing its re-oxidation to ferric iron (iron(III)). Once bound it is then taken up by the surrounding microbial community where it is used in photosynthesis and other metabolic processes. We strongly suspect that other key metals are similarly trapped and currently testing this idea. From an ecological standpoint, the sequestration of metals other than iron by EPS would make sense as this region has very low levels of biogenic metals such as copper and cobalt.
Recently, we have initiated a new series of studies examining the microbial diversity and ecology of South Carolina beaches. With the exception of beaches heavily impacted by large pollution events, little is known regarding the microbial ecology of these systems and the services that they provide to the near shore and estuarine marine ecosystem. New data are showing high levels of inorganic nitrogen compounds and ferrous iron. Microbiologically, we have detected members of the Planctomycetales, specifically those that are likely involved in nitrogen cycling. Ultimately we hope to link beach ecosystems to key ecological processes and issues associated with coastal life. Questions we are actively addressing include: Does the iron found in these beaches serve to fertilize the near shore ecosystem? What is the overall diversity found in a beach ecosystem? Are all SC beaches similar in their microbial diversity profiles? If not, what are the underlying parameters driving these differences? Are there any links (i.e. metals) between beach systems and the development of resistance in problematic bacteria found in the vicinity?
My laboratory is also involved in a collaborative effort with David Freedman’s laboratory (http://www.clemson.edu/ces/eees/people/facultydirectory/freedman.html) in Department of Environmental Engineering and Earth Sciences at Clemson University. This effort is directed at developing new processes and methods for the removal of chlorinated halocarbons such as chloroform, PCBs and polychlorinated benzenes from the environment. Currently our major efforts are on the remediation of chloroform, which reduces our ability to remediate other chlorinated compounds in the polluted system. We have had some success with this problem and are now exploring the possibility of improving this process using metabolic engineering. At this time, my laboratory is interested in detecting and identifying proteins that are specifically expressed when recently isolated bacterial strains, capable of degrading chloroform, are grown in the presence of chloroform. Through these efforts, we intend to determine the underlying biochemistry used by these bacteria to dechlorinate chloroform and convert it to CO.