Microbial diversity associated with metal- and radionuclide- contamination at the DOE Savannah River Site (SRS), South Carolina, USA

Abstract

The goal of this dissertation is to utilize an integrated approach of molecular microbiology (cloning, sequencing, and real-time PCR) and microbial lipid biomarker to understand microbial diversity, and the factors and mechanisms shaping microbial community structure in the heavily contaminated soils at the Savannah River Site of the US Department of Energy in South Carolina, USA. The first task of this dissertaton was to determine the effect of heavy metals (As, Co, Cr, Cu, Pb, and Ni) on the microbial diversity in the effluent channel of the waste water from a coal-generated power plant. The predominance of antibiotic resistant species near the source water indicated that heavy metal concentrations are likely to serve as selective pressure for antibiotic and metal tolerant bacteria and genes. Members of heterotrophic clostridia in D-area may directly participate in metal reduction or provide electron donors for the metal-reducing microorganisms. Another task was undertaken to examine the microbial community structures in heavy metal (eg. nickel) and radionuclides (eg., uranium) contaminated soils in the M-area. Members of sulfate-reducing and iron-reducing bacteria, especially Geobacter species may play an important role in immobilizing the metals and radionuclides in the uranium-contaminated sites. The third task was to determine the diversity and abundance of ammonium-oxidizing archaea in metal- and organic-contaminated soils at the Savannah River Site. To the best of my knowledge, this dissertation marks the first demonstration of microbial community changes in the heavily contaminated soils at the Savannah River Site, and demonstrated that the microbial community structure and abundance changed along with heavy metal and radionuclide gradients. This implies that it is feasible to bio-stimulate the indigenous microbial populations for bioremediation of contaminants at the Savannah River Site.