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Appl. Environ. Microbiol., May 1996, 1664-1669, Vol 62, No. 5
PR Dowdle, AM Laverman and RS Oremland
Incubation of anoxic salt marsh sediment slurries with 10 mM As(V) resulted
in the disappearance over time of the As(V) in conjunction with its
recovery as As(III). No As(V) reduction to As(III) occurred in
heat-sterilized or formalin-killed controls or in live sediments incubated
in air. The rate of As(V) reduction in slurries was enhanced by addition of
the electron donor lactate, H(inf2), or glucose, whereas the respiratory
inhibitor/uncoupler dinitrophenol, rotenone, or 2-heptyl-4-hydroxyquinoline
N-oxide blocked As(V) reduction. As(V) reduction was also inhibited by
tungstate but not by molybdate, sulfate, or phosphate. Nitrate inhibited
As(V) reduction by its action as a preferred respiratory electron acceptor
rather than as a structural analog of As(V). Nitrate-respiring sediments
could reduce As(V) to As(III) once all the nitrate was removed.
Chloramphenicol blocked the reduction of As(V) to As(III) in
nitrate-respiring sediments, suggesting that nitrate and arsenate were
reduced by separate enzyme systems. Oxidation of [2-(sup14)C]acetate to
(sup14)CO(inf2) by salt marsh and freshwater sediments was coupled to
As(V). Collectively, these results show that reduction of As(V) in
sediments proceeds by a dissimilatory process. Bacterial sulfate reduction
was completely inhibited by As(V) as well as by As(III).
Copyright © 1996, American Society for Microbiology
Bacterial Dissimilatory Reduction of Arsenic(V) to Arsenic(III) in Anoxic Sediments
U.S. Geological Survey, Menlo Park, California 94025, and Department of Biology, Free University of Amsterdam, Amsterdam 1081 HV, The Netherlands
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