Halorespiration of a Natural Organochlorine and Trichloroethylene in a Historically-Uncontaminated Soil

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NovakCBET-0966559Over the next 30 years, the EPA has estimated that 350,000 contaminated sites in the United States will require remediation at a projected cost of $250 billion. Halogenated pollutants are one of the most common sources of contamination at these sites. Microorganisms, called (de)halorespirers, have been identified that can reduce toxic chlorinated organics to less- or non-toxic compounds using chlorinated organics as electron acceptors for growth and energy. Although halorespirers have been shown to be marginally effective for bioremediation at some contaminated sites, the potential that these microorganisms hold remains unrealized. The PI recently discovered that Dehalococcoides-like microorganisms exist in uncontaminated soils at high numbers and that their concentration in the environment statistically correlates to the amount of natural chlorinated organic matter present. This discovery raises questions regarding the links between uncontaminated and contaminated environments. The research proposed herein will begin to address these links by examining the ability of organisms in uncontaminated soils to halorespire different chlorinated compounds, investigating the transcription of reductive dehalogenase (rdh) genes from uncontaminated soils during halorespiration, and determining how the rdh genes, gene transcripts, and bacterial communities change in uncontaminated soils upon exposure to anthropogenic chlorinated compounds. It is hypothesized that halorespirers from uncontaminated soils can respire both chlorinated xanthones and trichloroethylene and that the reductive dehalogenase enzymes used for the respiration of these two different compounds are homologous. This research will further our understanding of halorespiration, particularly in uncontaminated environments. This has critical implications for the remediation field, ecology, and geochemical cycling. The proposed research will provide a direct educational benefit for one graduate student and one undergraduate student, developing their experimental and critical thinking skills and helping them develop as engineers/scientists. In addition, results obtained in this research will be incorporated into the lecture notes of several classes, including Introduction to Environmental Engineering, a required course for undergraduate Civil Engineers at the University of Minnesota, and Environmental Microbiology, an upper-level undergraduate and lower-level graduate laboratory course. In particular, results from this project will be incorporated into lecture material on bioremediation and elemental cycling. Finally, if successful, this research could result in more rapid and successful remediation through the discovery of natural agents for use in bioaugmentation and biostimulation at contaminated sites.