| Abstract
| - The reduction of uranyl (U(VI)) to the relatively insolubletetravalent form (U(IV)) by Shewanella alga (BrY), adissimilatory metal-reducing bacteria, was studied in thepresence of environmentally relevant iron hydrous oxides.Because this process is dependent on U(VI) being usedas the terminal electron acceptor (TEA) during anaerobicrespiration, it is important to understand how otherpotential TEAs might affect this process. When cellsuspensions of BrY were added to uranyl acetate (400μM), uranyl was removed from solution within 10 h. Similarly,uranyl in the presence on goethite (11.1 μmol of U/m2 ofsolid) underwent dramatic reduction (>90%) with active BrYcells. In contrast, when ferrihydrite was available (0.67μmol of U/m2 of solid) only 48% of the initial U(VI) wasremoved after 10 h. When varying ratios of goethite andferrihydrite were incorporated into cell suspensions, the extentof uranyl reduction was inversely related to the fractionof ferrihydrite present. Increasing uranyl concentrationsretarded the inhibition, but the effects were transient. UsingRaman spectroscopy, we observed that the initial solidproduct was UO2.17, but with continued exposure to a reducingenvironment a relatively pure uraninite phase resulted.
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