2000 RESEARCH PROJECTS Program Element 2 Community Dynamics and Microbial Ecology PROJECT: Ecological Interactions Between Metals and Microbes That Impact Bioremediation PRINCIPAL INVESTIGATOR: Allan E. Konopka PROGRAM ELEMENT 2 Community Dynamics and Microbial Ecology The impact of lead and chromium contamination upon microbial community diversity and activity will be investigated at a site in Seymour IN we have identified. The site contains a gradient of contamination with Pb, Cr, and petroleum hydrocarbons. (1) Our previous work has led to the hypothesis that microscale heterogeneities in metal distribution impact the microbial community. This will be determined by mapping metal distribution at 10 µm resolution via an X-ray fluorescence microprobe, and by sequentially measuring microbial activity, microbial community diversity, and metal content on small soil samples. Microbial activities will be assessed by catabolism of 14-C substrates. Community structure will be determined by PCR amplification of a portion of the 16S rDNA gene, and separation of products on a denaturing gel. (2) Experiments in soil microcosms will be used to manipulate the bioavailability and homogeneity of metals; changes in microbial community and diversity will be determined. In addition, genetic techniques will be used to assess the potential role of the transfer of metal resistance genes in community responses. (3) Physiological and molecular analyses will be used to identify isolated microbes that can function to protect metal-sensitive microbes in situ or transfer metal resistance genes. (4) Because many sites contain toxic mixtures, an activity assay (3-H leucine incorporation) will be used to determine if the effects of different toxicants are independent, multiplicative, or additive. PROJECT: Distribution and Activity of Dissimilatory Metal-Reducing Microorganisms in Contaminated Subsurface Environments PRINCIPAL INVESTIGATOR: Derek R. Lovley PROGRAM ELEMENT 2 Community Dynamics and Microbial Ecology The reductive precipitation of contaminant metals such as uranium, technetium, chromium, and cobalt shows promise as a strategy for both intrinsic and engineered in situ bioremediation of Department of Energy sites contaminated with these metals. The reduction of these contaminant metals is intimately linked with the reduction of Fe(III), typically the most abundant microbially reducible metal in the subsurface. The objectives of the proposed studies are: 1) to determine which microbial populations are most important in metal reduction at contaminated DOE sites in which metal reduction is naturally occurring or in which metal reduction has been artificially stimulated; 2) to develop molecular tools to quantitatively assay the distribution and activity of these metal-reducing microorganisms; 3) to evaluate the physiological properties of metal-reducing microorganisms living in subsurface environments in order to better predict the rate and extent to which metals will be reduced under various conditions; and 4) to learn more about the diversity and physiological potential of metal-reducing microorganisms that may not necessarily be the most numerous in the subsurface, but may have unique physiological properties that could be useful in engineered metals bioremediation. These studies will provide a description of the microorganisms that are reducing metals at DOE sites as well as estimates of the in situ activity of these organisms. Furthermore, these studies are likely to recover microorganisms with novel bioremediation capabilities. This information will serve as the basis for a rational design of both intrinsic and engineered strategies for in situ remediation of metal-contaminated subsurface environments. PROJECT: Understanding the Roles of Spatial Iisolation and Carbon in Microbial Community Structure, Dynamics, and Activity for Bioremediation PRINCIPAL INVESTIGATOR: James M. Tiedje PROGRAM ELEMENT 2 Community Dynamics and Microbial Ecology The goal of this study is to establish a scientific foundation for improved in situ bioremediation of DOE contaminated sites through understanding the mechanisms that control structure, dynamics, and function of soil microbial communities. The following objectives will be pursued: (1) Determine the key relationships among soil texture, water content and carbon in controlling soil microbial communities; (2) Determine the impacts of radioactive and mixed-waste contaminants on the structure and composition of microbial communities and the effects of spatial isolation on the responses of microbial communities to such contaminants; (3) Develop and use microarray-based genomic technologies for analyzing microbial community structure, dynamics and activities. To achieve these objectives, we will test hypotheses about the role of spatial isolation, carbon heterogeneity and contaminants on microbial community structure and activities in the laboratory and at the NABIR Field Research Center. We will also develop novel microarray-based genomic technology to more comprehensively quantify microbial community dynamics. The genomic tools will also be used to analyze microbial community structure and activities in three multidisciplinary field studies. This research will be conducted as a collaborative project at Michigan State University and Oak Ridge National Laboratory. [Back to Award Recipients Page]