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Periplasmic cytochrome c3 of Desulfovibrio vulgaris is directly involved in H2-mediated metal but not sulfate reduction.

Abstract：

:Kinetic parameters and the role of cytochrome c(3) in sulfate, Fe(III), and U(VI) reduction were investigated in Desulfovibrio vulgaris Hildenborough. While sulfate reduction followed Michaelis-Menten kinetics (K(m) = 220 micro M), loss of Fe(III) and U(VI) was first-order at all concentrations tested. Initial reduction rates of all electron acceptors were similar for cells grown with H(2) and sulfate, while cultures grown using lactate and sulfate had similar rates of metal loss but lower sulfate reduction activities. The similarities in metal, but not sulfate, reduction with H(2) and lactate suggest divergent pathways. Respiration assays and reduced minus oxidized spectra were carried out to determine c-type cytochrome involvement in electron acceptor reduction. c-type cytochrome oxidation was immediate with Fe(III) and U(VI) in the presence of H(2), lactate, or pyruvate. Sulfidogenesis occurred with all three electron donors and effectively oxidized the c-type cytochrome in lactate- or pyruvate-reduced, but not H(2)-reduced cells. Correspondingly, electron acceptor competition assays with lactate or pyruvate as electron donors showed that Fe(III) inhibited U(VI) reduction, and U(VI) inhibited sulfate loss. However, sulfate reduction was slowed but not halted when H(2) was the electron donor in the presence of Fe(III) or U(VI). U(VI) loss was still impeded by Fe(III) when H(2) was used. Hence, we propose a modified pathway for the reduction of sulfate, Fe(III), and U(VI) which helps explain why these bacteria cannot grow using these metals. We further propose that cytochrome c(3) is an electron carrier involved in lactate and pyruvate oxidation and is the reductase for alternate electron acceptors with higher redox potentials than sulfate.

journal_name

Appl Environ Microbiol

journal_title

Applied and environmental microbiology

authors

Elias DA,Suflita JM,McInerney MJ,Krumholz LR

doi

10.1128/aem.70.1.413-420.2004

keywords:

subject

Has Abstract

pub_date

2004-01-01 00:00:00

pages

413-20

issue

eissn

0099-2240

issn

1098-5336

journal_volume

pub_type

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Periplasmic cytochrome c3 of Desulfovibrio vulgaris is directly involved in H2-mediated metal but not sulfate reduction.