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Pesticide-eating bacteria march on.

Bacteria that degrade toxic substances are nothing new, but microbiologist Jeffrey Karns of the ARS has just added two important examples to the list. Karns recently described how enzymes produced by Flavobacterium degrade coumaphos, a pesticide used to kill insect pests of livestock, and how Achromobacter enzymes degrade carbofuran, a pesticide used to control corn rootworm and other crop insects.

Coumaphos is a "recalcitrant" molecule that stays in the soil for a long time before being broken down. Although coumaphos is water insoluble and thus doesn't pollute groundwater, it can be toxic to living things while it remains in the soil.

Previous attempts to degrade coumaphos waste have focused on ozonation, exposure of the pesticide to ultraviolet light. This did not work, Karns says, because coumaphos is a turbid solution and could not be destroyed by the light. But he and his colleagues found that incubating the waste with Flavobacterium beforehand degrades it to chlorferon, a clearer solution that can then be further degraded by ozonation.

Carbofuran can be degraded by Achromobacter, a bacterial species that uses the pesticide as its only source of nitrogen, Karns says. These bacteria also degrade several other N-methyl carbamate insecticides, he says.

Karns is working on cloning the genes coding for the degradative enzymes of Flavobacterium and Achromobacter. "If this can be done," he says, "pesticide degradation will be more efficient because fewer [bacterial] cells will have to be used."
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Title Annotation:research on pesticide degradation
Publication:Science News
Date:May 25, 1985
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