Physiological and genetic mechanisms of bacterial resistance to environmental toxic metals and antibiotics Trace metal physiology: siderophores and natural chelating agents
Toxic Metal Bioremediation
I am conducting investigations in the bioremediation of environmental sites contaminated with toxic heavy metals. Our approach is to isolate toxic metal tolerant strains of bacteria and then to determine the physiological basis of the resistance mechanism. In so doing, conditions could then be optimized to construct bioreactor systems in an attempt to mitigate the heavy metal contaminant concentrations at various environmental sites. In conjunction with Dr. Keith Johnson, Visiting Assistant Professor of Biology, Colby College, we are studying the effects of environmental mercury in various systems (soil, lake trout gastrointestinal tract, and human oral cavity) and how this toxic metal is providing selective pressure in the evolution of mercury-resistant bacterial strains. In selecting for mercury-resistant microbial strains, the metal is also responsible for the co-selection of antibiotic-resistance determinants because genes responsible for both antibiotic- and mercury-resistance are linked genetically. Mercury is a by-product of various industrial applications, in particular it is found in emissions from coal-fired electrical generation plants in the Midwest. Atmospheric mercury is then deposited in the Maine environment via liquid precipitation. Hence, over time, not only does mercury pose a serious environmental health threat, bacterial strains are evolving that show an increased incidence of resistance to antibiotics. Conceivably, these genes could then be transferred horizontally to pathogens, making treatments of infectious disease with antibiotics non-efficacious.