The main goal of this PhD project is to pinpoint the gene and gene products that confer uranium resistance in C. metallidurans and, subsequently, to identify the underlying molecular mechanism. In order to determine these key genes, a previously acquired laboratory-evolved strain will be subjected to global genomic and transcriptomic analysis and candidate genes will be selected for further experimental validation via the construction of deletion, overexpression and complementation mutants. Functional analysis of the confirmed genes and their gene products, in combination with microscopy and spectrometry techniques, will allow us to determine the molecular mechanism underlying uranium resistance. In a next phase, the specificity of this response and adaptation to uranium will be evaluated by exposure of C. metallidurans to toxic concentrations of other long-lived natural radionuclides, such as thorium, and artificial radionuclides, such as U233 and americium. In contrast to studies performed until now regarding radionuclide resistance of microorganisms, this PhD will focus on the molecular mechanism driving the resistance and will also study elements other than U238, thereby, functionally identifying new genes and proteins, and pinpointing any radionuclide-specific adaptation process. Understanding the precise cellular response is necessary to investigate their potential in bioremediation purposes.
1. Simonoff, M., et al., Microorganisms and migration of radionuclides in environment. Comptes Rendus Chimie, 2007. 10(10-11): p. 1092-1107.
2. Choudhary, S., et al., Uranium and other heavy metal resistance and accumulation in bacteria isolated from uranium mine wastes. Journal of Environmental Science and Health Part a-Toxic/Hazardous Substances & Environmental Engineering, 2012. 474): p. 622-637.
3. Ding, C.C., et al., Biosorption behavior and mechanism of thorium on Streptomyces sporoverrucosus dwc-3. Journal of Radioanalytical and Nuclear Chemistry, 2014. 301(1): p. 237-245.
4. Payne, R.B., et al., Interaction between uranium and the cytochrome c(3) of Desulfovibrio desulfuricans strain G20. Archives of Microbiology, 2004. 181(6): p. 398-406.
5. Merroun, M.L. and S. Selenska-Pobell, Bacterial interactions with uranium: An environmental perspective. Journal of Contaminant Hydrology, 2008. 102(3-4): p. 285-295.
6. Macaskie, L.E., B.C. Jeong, and M.R. Tolley, Enzymically accelerated biomineralization of heavy metals: application to the removal of americium and plutonium from aqueous flows. FEMS Microbiol Rev, 1994. 14(4): p. 351-67.
7. Llorens, I., et al., Uranium Interaction with Two Multi-Resistant Environmental Bacteria: Cupriavidus metallidurans CH34 and Rhodopseudomonas palustris.Plos One, 2012. 7(12).
8. De Borba, T.R., et al. Application of Bacteria to Remove Americium from Radioactive Liquid Waste. In WM2011 Conference. 2011. Phoenix, AZ.