(Georgia Institute of Technology, 2008-06-23)
Martinez, Robert J.
Extreme environments created through natural and anthropogenic processes harbor microbes with diverse physiologies capable of catalyzing chemical reactions which are environmentally beneficial on local and global scales. This work focused on two unique environments, the Gulf of Mexico (GoM) submarine mud volcano systems and the subsurface soils at the Department of Energy s (DOE) Field Research Center (FRC) located in the Oak Ridge National Laboratory Reservation (Oak Ridge, TN). In addition to the physical and chemical extremes present within mud volcano sediments and FRC subsurface soils, these environments are sources of greenhouse gases as well as metal/radionuclide contaminants, respectively. Within the previously uncharacterized mud volcano cold seep sediments, culture-independent analyses of microbial community structure via DNA and RNA clone libraries indicated Gammaproteobacteria and anaerobic methane oxidizing Archaea as the dominant methane oxidizing taxa. Culture-dependent studies of FRC subsurface Arthrobacter and Bacillus isolates demonstrated extensive lateral gene transfer of the PIB-type ATPase metal resistance genes. Additionally, FRC Bacillus and Rahnella isolates demonstrated U(VI) sequestration capabilities as up to 95% soluble U(VI) was immobilization via biogenic phosphate mineral production resulting from constitutive nonspecific phosphohydrolase activity. Findings from these studies identify the prokaryotic diversity within aquatic and terrestrial sediments that contribute to the geochemical cycling of carbon, metals, and radionuclides.