title: In vitro reduction of hexavalent chromium by a cell-free extract of Bacillus sp. ES 29 stimulated by Cu2+.
abstract: Chromium-resistant bacteria (CRB) isolated from soils can be used to reduce toxic Cr(VI) from contaminated environments. This study assessed in vitro reduction of hexavalent Cr using a cell-free extract (CFE) of CRB isolated from soil contaminated with dichromate. One isolate, ES 29, that substantially reduced Cr(VI) was identified as a Bacillus species by 16S rRNA gene-sequence homology. The isolate reduced Cr(VI) under aerobic conditions, using NADH as an electron donor and produced a soluble Cr(VI)-reducing enzyme stimulated by copper (Cu2+). The CFE of the bacterial isolate reduced 50% of Cr(VI) in 6 h. The Cr(VI)-reduction activity of the CFE had a Km of 7.09 microM and a Vmax of 0.171 micromol min(-1) mg(-1) protein. Mercury inhibited the enzyme, but not competitively, with a Vmax of 0.143 micromol min(-1) mg(-1) protein, a Km of 7.07 microM and a Ki of 1.58 microM. This study characterizes the enzymatic reduction of Cr(VI) by Bacillus sp. ES 29 which can be used for the bioremediation of chromate.
authors.affiliation: Department of Environmental Science, University of California, Riverside, CA 92521, USA.
authors.forename: F A O
authors.initials: FA
authors.lastname: Camargo
authors.forename: B C
authors.initials: BC
authors.lastname: Okeke
authors.forename: F M
authors.initials: FM
authors.lastname: Bento
authors.forename: W T
authors.initials: WT
authors.lastname: Frankenberger
mesh_terms: D001407:Bacillus / Q000145:classification / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D001673:Biodegradation, Environmental; D002458:Cell Fractionation; D002857:Chromium / Q000378:metabolism* / Q000633:toxicity; D003300:Copper / Q000378:metabolism*; D024881:Drug Resistance, Bacterial; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008628:Mercury / Q000494:pharmacology; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011192:Potassium Dichromate; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D012989:Soil Pollutants; D002857:Chromium; D009243:NAD; C074702:chromium hexavalent ion; D003300:Copper; D010088:Oxidoreductases; C075965:chromium(VI) reductase; D008628:Mercury; D011192:Potassium Dichromate