Date of Award


Degree Name

Master of Science



First Advisor

Dr. Johnson R. Haas

Second Advisor

Dr. Carla M. Koretsky

Third Advisor

Dr. Alan E. Kehew

Access Setting

Masters Thesis-Open Access


Haas and DiChristina (2002) have demonstrated that Fe(III) reduction by the facultative Fe(III)-reducing bacterium S. putrefaciens is mediated by competitive speciation among dissolved organic ligands and functional groups on the cell surface. They also showed that rates of Fe(III) reduction by S. putrefaciens correlate with the thermodynamic stability constants of the Fe(III)-organic ligand complexes. S. putrefaciens can also use U(VI) as a terminal electron acceptor, coupling U(VI) reduction to growth. In this study, S. putrefaciens was incubated in experimental media containing U(VI) in the form of aqueous complexes with a variety of organic ligands that differ significantly in structure and stability with respect to U(VI) chelation. Rates of U(VI) reduction by S. putrefaciens vary strongly as a function of U(VI) aqueous speciation. The results of this study indicate that U(VI) reduction under field conditions may be inhibited by the presence of organic chelating ligands.

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