Ferric iron reduction by Desulfovibrio vulgaris Hildenborough wild type and energy metabolism mutants |
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Authors: | Hyung Soo Park Shiping Lin Gerrit Voordouw |
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Institution: | (1) Department of Biological Sciences, University of Calgary, Calgary, AB, Canada, T2N 1N4 |
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Abstract: | Desulfovibrio vulgaris Hildenborough wild type and its hyn1, hyd and hmc mutants, lacking genes for periplasmic NiFe] hydrogenase-1, periplasmic FeFe] hydrogenase or the transmembrane high molecular
weight cytochrome (Hmc) complex, respectively, were able to reduce Fe(III) chelated with nitrilotriacetic acid (NTA), but
not insoluble ferric oxide, with lactate as the electron donor. The rate and extent of Fe(III)-NTA reduction followed the
order hyn = WT > hmc >> hyd, suggesting that reduction of soluble Fe(III) is a periplasmic process that requires the presence of periplasmic FeFe] hydrogenase.
Reduction of Fe(III)-NTA was not coupled to cell growth. In fact cell concentrations declined when D. vulgaris was incubated with Fe(III)-NTA as the only electron acceptor. Wild type and mutant cells reducing a limiting concentration
of sulfate (2 mM), reduced Fe(III)-NTA with similar rates. However, these were similarly incapable of catalyzing subsequent
lactate-dependent reduction of Fe(III)-NTA to completion. Periplasmic reduction of Fe(III)-NTA appeared to inhibit the productive,
sulfate-reducing metabolism of D. vulgaris, possibly because it prevents the cycling of reducing equivalents needed to achieve a net bioenergetic benefit. |
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Keywords: | Desulfovibrio Sulfate-reducing bacteria Ferrihydrate Hydrogenase Fe(III) reduction |
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