Chromium(VI) reductase activity is associated with the cytoplasmic membrane of anaerobically grown Shewanella putrefaciens MR-1.
Shewanella putrefaciens MR-1 can reduce a diverse array of compounds under anaerobic conditions, including manganese and iron oxides, fumarate, nitrate, and many other compounds. These reductive processes are apparently linked to a complex electron transport system. Chromium (Cr) is a toxic and mutagenic metal and bacteria could potentially be utilized to immobilize Cr by reducing the soluble and bioavailable state, Cr(VI), to the insoluble and less bioavailable state, Cr(III). Formate-dependent Cr(VI) reductase activity was detected in anaerobically grown cells of S. putrefaciens MR-1, with highest specific activity in the cytoplasmic membrane. Both formate and NADH served as electron donors for Cr(VI) reductase, whereas L-lactate or NADPH did not support any activity. The addition of 10 micromol l(-1) FMN markedly stimulated formate-dependent Cr(VI) reductase, and the activity was almost completely inhibited by diphenyliodonium chloride, an inhibitor of flavoproteins. Cr(VI) reductase activity was also inhibited by p-chloromercuriphenylsulphonate, azide, 2-heptyl-4-hydroxyquinolone-N-oxide, and antimycin A, suggesting involvement of a multi-component electron transport chain which could include cytochromes and quinones. Cr(V) was detected by electron paramagnetic resonance (EPR) spectroscopy, suggesting a one-electron reduction as the first step.
Myers
C R
CR
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee 53226, USA.
Carstens
B P
BP
Antholine
W E
WE
Myers
J M
JM
D000693:Anaerobiosis; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005486:Flavin Mononucleotide / Q000378:metabolism; D005561:Formates / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020614:Shewanella putrefaciens / Q000201:enzymology* / Q000378:metabolism
D004791:Enzyme Inhibitors; D005561:Formates; D009243:NAD; C030544:formic acid; D005486:Flavin Mononucleotide; D010088:Oxidoreductases; C075965:chromium(VI) reductase