Understanding biological uranium reduction Sherilee Palm Energy Postgraduate Conference 2013 Supervisor: Prof E. van Heerden Co-supervisors: Errol Cason Dr. D. Opperman

Introduction Microbe – metal interactions: Systems Bioaccumulation Biomineralization Biosorption Bioreduction (Beliaev et al., 2001)

Introduction (Vaughan and Lloyd, 2011)

Aims Assess the microbial diversity of uranium and thorium contaminated water. Use metal-reducing bacteria as biocatalysts for uranium and thorium bioreduction. Use known genomes of metal reducers to elucidate metabolic capabilities.

Diversity

To understand how a biological process occurs, two routes can be followed: Let the microorganism do the work Assess the genome of the microorganism to determine if it has the correct tools to do the work.

Uranium reduction U (IV)U (VI) –Mobile –Soluble –Toxic Mutagen & carcinogenic U(IV) –Immobile –Insoluble –Less toxic (Payne, 2005; Cason et al., 2012; Abdelouas et al., 2000)

Enzymatic U(VI) reduction The Lovley Model: (Lovley et al., 1993; Cason et al., 2012 ) Peptide ABC transporter, peptide-binding protein

External electron transport systems (Valocchi, 2011)

Conclusions Microbial encounters with metals in the environment are inevitable, consequently microbes have developed defence mechanisms against metal toxicity. A mechanistic understanding of uranium (and thorium) bioreduction/biosorption could aid in devising an effective and economically feasible bioremediation process for the removal/separation of these metals.

Acknowledgements University if the Free State Prof Esta van Heerden Extreme biochemistry NRF (SANHARP)

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