Reduction of Cr(VI) under acidic conditions by the facultative Fe(III)-reducing bacterium Acidiphilium cryptum

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es061333k· OSTI ID:912300

Cummings, David E; Fendorf, Scott; Sani, Rajesh K; Peyton, Brent M; Magnuson, Timothy S

The potential for biological reduction of Cr(VI) under acidic conditions was evaluated with the acidophilic, facultatively metal-reducing bacterium Acidiphilium cryptum strain JF-5 to explore the role of acidophilic microorganisms in the Cr cycle in low-pH environments. An anaerobic suspension of washed A. cryptum cells rapidly reduced 50 M Cr(VI) at pH 3.2; biological reduction was detected from pH 1.7-4.7. The reduction product, confirmed by XANES analysis, was entirely Cr(III) that was associated predominantly with the cell biomass (70-80%) with the residual residing in the aqueous phase. Reduction of Cr(VI) showed a pH optimum similar to that for growth and was inhibited by 5 mM HgCl2, suggesting that the reaction was enzyme-mediated. Introduction of O2 into the reaction medium slowed the reduction rate only slightly, whereas soluble Fe(III) (as ferric sulfate) increased the rate dramatically, presumably by the shuttling of electrons from bioreduced Fe(II) to Cr(VI) in a coupled biotic-abiotic cycle. Starved cells could not reduce Cr(VI) when provided as sole electron acceptor, indicating that Cr(VI) reduction is not an energy-conserving process in A. cryptum. We speculate, rather, that Cr(VI) reduction is used here as a detoxification mechanism.

• Research Organization: Idaho National Laboratory (INL)
• Sponsoring Organization: DOE - EM
• DOE Contract Number: AC07-99ID13727
• OSTI ID: 912300
• Report Number(s): INEEL/JOU-04-02176
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 1 Vol. 41; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BINDING ENERGY
BIOMASS
DETOXIFICATION
ELECTRONS
MICROORGANISMS
STRAINS
VALENCE