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Appl. Environ. Microbiol., Mar 1995, 953-958, Vol 61, No. 3
DR Lovley, JD Coates, JC Woodward and EJP Phillips
Highly reduced sediments from San Diego Bay, Calif., that were incubated
under strictly anaerobic conditions metabolized benzene within 55 days when
they were exposed initially to 1 (mu)M benzene. The rate of benzene
metabolism increased as benzene was added back to the benzene-adapted
sediments. When a [(sup14)C]benzene tracer was included with the benzene
added to benzene-adapted sediments, 92% of the added radioactivity was
recovered as (sup14)CO(inf2). Molybdate, an inhibitor of sulfate reduction,
inhibited benzene uptake and production of (sup14)CO(inf2) from
[(sup14)C]benzene. Benzene metabolism stopped when the sediments became
sulfate depleted, and benzene uptake resumed when sulfate was added again.
The stoichiometry of benzene uptake and sulfate reduction was consistent
with the hypothesis that sulfate was the principal electron acceptor for
benzene oxidation. Isotope trapping experiments performed with
[(sup14)C]benzene revealed that there was no production of such potential
extracellular intermediates of benzene oxidation as phenol, benzoate,
p-hydroxybenzoate, cyclohexane, catechol, and acetate. The results
demonstrate that benzene can be oxidized in the absence of O(inf2), with
sulfate serving as the electron acceptor, and suggest that some sulfate
reducers are capable of completely oxidizing benzene to carbon dioxide
without the production of extracellular intermediates. Although anaerobic
benzene oxidation coupled to chelated Fe(III) has been documented
previously, the study reported here provides the first example of a natural
sediment compound that can serve as an electron acceptor for anaerobic
benzene oxidation.
Copyright © 1995, American Society for Microbiology
Benzene Oxidation Coupled to Sulfate Reduction
U.S. Geological Survey, Reston, Virginia 22092
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