Final Technical Report: Optimization and Directed, Natural Evolution of Biologically-Mediated Chromate Reduction in Subsurface Soil Microcosms
The U.S. Department of Energy (DOE) is faced with the complex challenge of remediating or containing the various mixed wastes present in the subsurface environments of numerous DOE sites. The development of scientifically grounded strategies for the effective management and reclamation of these contaminated sites requires fundamental knowledge on the composition, dynamics, and metabolic potential of indigenous microbial communities, which are of primary importance in the fate and transport of heavy metals and radionuclides in subsurface environments. To date, the complex effect of environmental (both geochemical and biological) parameters on the bioremediative potential of subsurface microbial populations is only partially understood; this is primarily because the majority of microbial ecological studies have focused only on a qualitative analysis of subsurface microbial diversity, while the impact of quantitative changes in microbial communities as a function of environmental factors has been ignored. The project described here directly addresses the need for a more comprehensive, molecular understanding of how microbial growth and activity quantitatively relate to mineral and contaminant biotransformation (Science Element: Subsurface Microbial Ecology and Community, Notice DE-FG02-06ER06-12). The proposed study uses a truly novel combination of standard molecular phylogenetic analyses, rRNA-targeted fluorescence in situ hybridization, and mass spectrometry (MS)-based proteomics to investigate the biological response to experimentally controlled conditions and the concomitant effect on chromate reduction in situ. This response will be characterized in terms of microbial community structure (principally, population number and spatial distribution) and community proteome dynamics. Towards this overarching goal, we will (1) set up aerobic and anaerobic laboratory microcosms derived from subsurface soil collected from a chromate [Cr(VI)]-contaminated DOE site, and introduce Cr(VI)-reducing Pseudomonas putida (a facultative anaerobe) and/or Desulfovibrio desulfuricans (an obligate anaerobe) into the extant microbial community of each microcosm (Objective 1); (2) determine the qualitative and quantitative effects of organic carbon amendments on microcosm community structure, metabolic activity, and, most importantly, biologically-mediated chromate reduction (Objective 2); and (3) investigate the microbial community response from molecular and quantitative perspectives in microcosms challenged with increasing levels of chromate in order to drive selection of chromate-reducing populations (Objective 3). The proposed project is a collaborative endeavor among scientists from Purdue University and Oak Ridge National Laboratory. A unique aspect of this project is the application of shotgun MS techniques as molecular ecology tools for metabolically profiling targeted microbial species within the context of complex environmental communities and searching for unique or abundant proteins that might serve as indicators for heavy metal stress and reduction in microsites. Studies such as this one that tackle the challenge of characterizing the proteome dataset of a complex microbial microcosm will be needed to push the capabilities of current MS methodologies and to develop the next generation of microbial ecology tools of use in assessing bioremediation performance. We expect that the experimental protocols and results generated in this project will expand our quantitative and mechanistic understanding of the in situ biological contributions to metal contaminant transformation.
- Research Organization:
- University of Tennessee (Knoxville)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- SC0003854
- OSTI ID:
- 1046926
- Report Number(s):
- R012580235
- Country of Publication:
- United States
- Language:
- English
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