title: Formation of soluble organo-chromium(III) complexes after chromate reduction in the presence of cellular organics.
abstract: Microbial reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] has been investigated as a method for bioremediation of Cr(VI) contaminated environments. The produced Cr(III) is thought to be insoluble Cr(OH)3; however, recent reports suggested a more complex fate of Cr(III). A bacterial enzyme system, using NADH as the reductant, converts Cr(VI)to a soluble NAD+-Cr(III) complex, and cytochrome c-mediated Cr(VI) reduction produces cytochrome c-Cr(III) adducts. In this study, Cr(VI) reduction in the presence of cellular organic metabolites formed both soluble and insoluble organo-Cr(III) end-products. Several soluble end-products were characterized by absorbance spectroscopy and electron paramagnetic resonance spectrometry as organo-Cr(III) complexes, similar to the known ascorbate-Cr(III) complex. The complexes remained soluble and stable upon dialysis against distilled H20 and over a broad pH range. The ready formation of stable organo-Cr(III) complexes suggests that organo-Cr(III) complexes are rather common, likely representing an integral part of the natural cycling of chromium. Thus, organo-Cr(III) complexes may account for the mobile form of Cr(II) detected in the environment.
authors.affiliation: School of Molecular Biosciences, Center for Multiphase Environmental Research, and Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA.
authors.forename: Geoffrey J
authors.initials: GJ
authors.lastname: Puzon
authors.forename: Arthur G
authors.initials: AG
authors.lastname: Roberts
authors.forename: David M
authors.initials: DM
authors.lastname: Kramer
authors.forename: Luying
authors.initials: L
authors.lastname: Xun
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism; D001673:Biodegradation, Environmental; D002840:Chromates / Q000737:chemistry / Q000378:metabolism*; D002857:Chromium / Q000737:chemistry / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D012995:Solubility
chemical_list: D002840:Chromates; D012989:Soil Pollutants; D002857:Chromium; D009243:NAD; D045304:Cytochromes c; D001205:Ascorbic Acid