Chlorinated aliphatic hydrocarbons, such as tetrachloroethene (PCE) and trichloroethene (TCE) are the most abundant groundwater contaminants of US aquifers. While bioremediation of these pollutants via reductively dehalogenating microorganisms has been successful at many sites, there are numerous sites where the success has been limited. This limited success is frequently due to a lack of understanding of in situ microbial reductive dehalogenation and complex biogeochemical processes. Dehalococcoides mccartyi (Dhc) species appear to be the most important microbes for complete dechlorination of PCE and TCE to the harmless ethene. As members of the rare, slow growing biosphere, Dehalococcoides sp. are strictly anaerobic microbes, are highly niche-adapted to reductive dehalogenation, are difficult to isolate in pure culture, and are metabolically integrated in unknown ways into a supporting microbial community. This collaborative, interdisciplinary engineering and science research will provide a fundamental understanding of the dynamics of slow growing, reductively dehalogenating microbes, their populations, and the associated microbial communities during reductive dehalogenation of chloroethenes at fluctuating low concentrations of hydrogen their preferred electron donor. A better understanding will be achieved by a combined approach consisting of experimentally determining molecular and organismal properties of the competition for hydrogen by different microbes of a dehalogenating community and of developing a predictive mathematical model to simulate the competition for hydrogen among the microbial community. The expected outcome is a deeper systems-level understanding of how in a natural microbial ecosystem, dynamically changing diverse electron donors and alternate electron acceptors cause shifts in composition of the microbial community and populations of dehalogenating microbes.
Broader Impacts. The broader impacts of this research will be on three levels: 1) Successful engineering of microbial reductive dehalogenation for bioremediation of groundwater contaminated with chloroethenes. The collaborative interdisciplinary research will provide insights into crucial data and modeling needed for engineering more efficient bioremediation systems. This type of combined molecular/experimental, statistical and mathematical approach is expected to be transferable for engineering the remediation of other high priority environmental contaminants, such fluorohydrocarbons, heavy metals, or radionuclides; 2) Fundamental insights will be obtained into the (eco) physiological dynamics and natural population structure of Dehalococcoides sp. which are members of the highly-niche adapted, rare, slow growing biosphere. Studies will enable scientists to begin to frame and answer some crucial questions on the biology of such microbes and on life under low-growth conditions in general; 3) The students involved in this project will be trained in microbial physiology and molecular methods, statistical methods for the analysis of molecular information, in environmental engineering and in mathematical modeling of biological or geochemical systems. The students will learn the fundamentals either in engineering or microbiology as their core discipline, and will also be trained in using statistical methods and modeling to educate the next generation of collaborative microbiologists and environmental engineers.
