Iron Promoted Reduction of Chromate by Dissimilatory Iron-Reducing Bacteria

Abstract

Chromate is a priority pollutant within the U.S. and many other countries, the hazard of which can be mitigated by reduction to the trivalent form of chromium. Here we elucidate the 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 containing Shewanella alga strain BrY and iron (hydr)oxides of varying stabilities results in complete reduction to Cr(III). The maximum sustainable Cr(VI) reduction rate was 5.5 micrograms CrVI.mg-cell-1.h-1 within ferric (hydr)oxide suspensions (surface area 10 m2). In iron limited systems (having HEPES as a buffer), iron was cycled suggesting it acts in a catalytic-type manner for the bacterial reduction of Cr(VI). BrY also 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 primary pathway for the sequestration and detoxification of chromate in anaerobic soils and water.

Microbial interspecies electron transfer via electric currents through conductive minerals

“…Iron works as an electron shuttle in microbial ecosystems (20,27). In the coculture of G. sulfurreducens and T. denitrificans, the data (Fig.…”

Reductive immobilization of U(VI) in Fe(III) oxide-reducing subsurface sediments: Analysis of coupled microbial-geochemical processes in experimental reactive transport systems

“…layered silicates and/or residual Fe(III) oxide surfaces) is capable of promoting rapid abiotic contaminant reduction, then it should be possible to achieve effective remediation through only periodic stimulation of DMRB activity so as to renew the capacity of the sediment for Fe(II)-promoted contaminant reduction. Such a strategy is likely to be effective in the case of Cr(VI) remediation, since both aqueous and surface-bound Fe(II) produced during bacterial Fe(III) oxide reduction are excellent reductants for soluble CrO 4 2-ions (Wielinga et al, 2001). In contrast, the potential for Fe(II)-promoted abiotic reduction of U(VI) is less certain.…”

Treatability Study of In Situ Technologies for Remediation of Hexavalent Chromium in Groundwater at the Puchack Well Field Superfund Site, New Jersey

“…Amorphous iron sulfide produced by sulfate reduction has also been shown to reduce Cr(VI) (Patterson and Fendorf 1997 whereby the reduction product is a mixed Cr, Fe precipitate that is also produced under reduced iron conditions. Compared to the rate of direct enzymatic reduction of Cr(VI), reduction by Fe(II) or sulfide appear to be significantly faster (Wielinga et al 2001). However, microbial processes can play a key role in producing and maintaining reduced iron and sulfide in the aquifer.…”