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Appl. Environ. Microbiol., Sep 1997, 3594-3599, Vol 63, No. 9
GT Townsend and JM Suflita
The inhibition of aryl reductive dehalogenation reactions by sulfur
oxyanions has been demonstrated in environmental samples, dehalogenating
enrichments, and the sulfate-reducing bacterium Desulfomonile tiedjei;
however, this phenomenon is not well understood. We examined the effects of
sulfate, sulfite, and thiosulfate on reductive dehalogenation in the model
microorganism D. tiedjei and found separate mechanisms of inhibition due to
these oxyanions under growth versus nongrowth conditions. Dehalogenation
activity was greatly reduced in extracts of cells grown in the presence of
both 3- chlorobenzoate, the substrate or inducer for the aryl
dehalogenation activity, and either sulfate, sulfite, or thiosulfate,
indicating that sulfur oxyanions repress the requisite enzymes. In extracts
of fully induced cells, thiosulfate and sulfite, but not sulfate, were
potent inhibitors of aryl dehalogenation activity even in membrane
fractions lacking the cytoplasmically located sulfur oxyanion reductase.
These results suggest that under growth conditions, sulfur oxyanions serve
as preferred electron acceptors and negatively influence dehalogenation
activity in D. tiedjei by regulating the amount of active aryl dehalogenase
in cells. Additionally, in vitro inhibition by sulfur oxyanions is due to
the interaction of the reactive species with enzymes involved in
dehalogenation and need not involve competition between two respiratory
processes for reducing equivalents. Sulfur oxyanions also inhibited
tetrachloroethylene dehalogenation by the same mechanisms, further
indicating that chloroethylenes are fortuitously dehalogenated by the aryl
dehalogenase. The commonly observed inhibition of reductive dehalogenation
reactions under sulfate-reducing conditions may be due to similar
regulation mechanisms in other dehalogenating microorganisms that contain
multiple respiratory activities.
Copyright © 1997, American Society for Microbiology
Influence of sulfur oxyanions on reductive dehalogenation activities in Desulfomonile tiedjei
Department of Botany and Microbiology, University of Oklahoma, Norman 73019, USA.
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