| Abstract
| - Chromate is a priority pollutant within the U.S. and manyother countries, the hazard of which can be mitigated byreduction to the trivalent form of chromium. Here we elucidatethe reduction of Cr(VI) to Cr(III) via a closely coupled, biotic−abiotic reductive pathway under iron-reducing conditions.Injection of chromate into stirred-flow reactors containingShewanella alga strain BrY and iron (hydr)oxides ofvarying stabilities results in complete reduction to Cr(III).The maximum sustainable Cr(VI) reduction rate was 5.5 μgCrVI·mg-cell-1·h-1 within ferric (hydr)oxide suspensions(surface area 10 m2). In iron limited systems (having HEPESas a buffer), iron was cycled suggesting it acts in a catalytic-type manner for the bacterial reduction of Cr(VI). BrYalso reduced Cr(VI) directly; however, the rate of direct(enzymatic) reduction is considerably slower than by Fe(II)(aq)and is inhibited within 20 h due to chromate toxicity.Thus, dissimilatory iron reduction may provide a primarypathway for the sequestration and detoxification of chromatein anaerobic soils and water.
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