Physiology of Nitrate-reducing Strains Cultivated from Contaminated Groundwater at the Oak-ridge Field Research Center
Tuesday, 16 December 2014
The groundwater at the U.S. Department of Energy’s Field Research Center (FRC) in Oak Ridge contains plumes of nitrate with concentrations up to 14,000mg/L among other contaminants. We isolated hundreds of nitrate-reducing bacteria (NRB) from groundwater wells across these geochemical gradients to better understand the diversity, physiology and regulation of nitrate reduction. Isolated NRB were representatives from Pseudomonas, Castellaniella, Rhodanobacter, Intrasporangium, Aquaspirillum, Variovorax, Duganella, Delftia, Chromobacter, Cupriavidus, Dechloromonas and Polaromonas genera among others. Within the Pseudomonas genus, more than a dozen different species were isolated. While some of Pseudomonas strains grew robustly in the presence of high concentrations of nitrate (300mM), others did not. Analysis of their genomes revealed that each strain contains circa 1000 genes distinct from each other- some of them being in denitrification-related genes. Molybdenum is an important metal cofactor of denitrification, and we hypothesize that nitrate-reduction by these strains is regulated by Mo at the genomic and protein level. Furthermore, several of these strains could oxidize humics coupled to denitrification. We present results from our ongoing genotypic, phenotypic characterization of nitrate-reducing isolates from FRC.