We are interested in microbial ecology and environmental microbiology and our research program is focused on the interactions of microorganisms and communities with toxic heavy metals. Our investigation spans a broad range of topics, from fundamental issues such as the origin and evolution of metal resistance and the role of horizontal gene transfer in metal resistance, to applied aspects of microbe-metal interactions such as bioremediation of contaminated environments. Most of our current work is focused on the interactions of microbes with mercury and it is tightly connected with the biogeochemical cycle of mercury (Figure 1).
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The biogeochemistry of Hg has received considerable attention because of the toxicity of methylmercury, the accumulation of methylmercury in biota, and its biomagnification in aquatic food chains. Knowledge of the concentration, transport, and dynamics of Hg in its various chemical forms in ecosystems is needed to predict its potential impact on human being and ecosystems. Our research combines biogeochemical, microbiological, and molecular investigations of the transformations of mercury (and of the microbes that carry them out) to study factors that control Hg cycling and transport of Hg in the environment. Our studies combine examinations of intact environmental samples and of microorganisms in pure cultures that we, and others, have isolated from various environments.
A system that we study extensively is the mercury resistance (mer) system, which is common among many microbes. The details of this system and how it works is shown in (Figure 2).
Figure. 2: The mercury resistance (mer) operon consists of gnes that encode for the transport of mercury into the cell(merT, P, C). those encoding for the degradtion of oranomercury compounds (merB) and reduction of ionic to elemental mercury (merA) and for regulatory funtions (merR.D). When mercury enters the cell it induces expresion of the mer operon leading to degradation of organomercury and reduction of ionic mercury to the volatile elemental form, whic is transported away from the cell. Thus, the mer systerm leads to mercury detoxification