Degradation of the Selective Herbicide 2,2-Dichloropropionate (Dalapon) by a Soil Bacterium

Abstract

Summary: A bacterium capable of utilizing the selective herbicide 2,2-dichloropropionate (Dalapon) as sole source of carbon and energy was isolated from soil and tentatively identified as a fast-growing species of Rhizobium. 2-Chloropropionate also supported good growth of the organism but 3-chloropropionate, monochloroacetate and dichloroacetate were not utilized. Bacteria grown in the presence of either 2,2-dichloropropionate or 2-chloropropionate oxidized these compounds and a variety of non-chlorinated substrates but not monochloroacetate. Cell-free extracts of 2,2-dichloropropionate-grown bacteria converted 2,2-dichloropropionate into pyruvate with the concomitant release of two chloride ions for each molecule of pyruvate formed, indicating the presence of dehalogenase activity. Dichloroacetate and 2-chloropropionate were also inducers and substrates for the dehalogenase. Monochloroacetate was a substrate for the dehalogenase but did not serve as an inducer whereas 3-chloropropionate was a non-substrate inducer.