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Biomolecular Mechanisms Controlling Metal and Radionuclide Transformations in Anaeromyxobacter dehalogenans

Alex Beliaev, Principal Investigator

Microbiological reduction of uranium(VI) and technetium(VII) has been proposed as a strategy for remediating radionuclide-contaminated environments. Numerous studies focusing on the reduction kinetics of and speciation induced by these metals have been carried out using contaminated sediment samples, microbial consortia, and pure bacterial cultures. While previous work with model organisms has increased the general understanding of radionuclide transformation processes, fundamental questions regarding radionuclide reduction mechanisms by indigenous microorganisms are poorly understood. This is especially true under the common scenario in which multiple electron acceptors are present. The goals of the Biomolecular Mechanisms Controlling Metal and Radionuclide Transformations in Anaeromyxobacter dehalogenans project team at Pacific Northwest National Laboratory (PNNL) are to elucidate the molecular mechanisms of radionuclide biotransformation used by Anaeromyxobacter dehalogenans(A. dehalogenans) and to assess the effects of relevant environmental factors on these transformation reactions.

Members of the Anaeromyxobactergenus have been found in a range of undisturbed and contaminated soils and sediments. Importantly, Anaeromyxobacter species were shown to occur in the uranium(VI)-contaminated, acidic sediments of the Environmental Remediation Sciences Program (ERSP) Field Research Center (FRC) in Oak Ridge, Tennessee . We are integrating targeted physiological and genetic analyses with microarray expression and genotype profiling to elucidate the mechanisms of metal transformation reactions in A. dehalogenans. The distribution and diversity of genes involved in metal and radionuclide reduction among different A. dehalogenans strains, including those detected in enrichment cultures derived from FRC site material, are being assessed using a microarray-based comparative genomics approach. Further, we are determining the effects of co-contaminants, such as nitrate and chlorinated solvents, on radionuclide reduction. To provide samples of high quality for our research, we are using established chemostat cultivation techniques to produce cells under precisely controlled and defined conditions.

Our research will generate a novel understanding of the mechanisms involved in metal reduction and enhance our capability to predict the processes that govern radionuclide transformation reactions in subsurface environments. Ultimately, these findings will assist the design and implementation of more efficient bioremediation approaches to enhance the reductive transformation and immobilization of radionuclides at contaminated U.S. Department of Energy sites.

Information regarding the Biomolecular Mechanisms Controlling Metal and Radionuclide Transformations in Anaeromyxobacter dehalogenans project was obtained from its ERSP project page.

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