METABOLISM OF CARBAMOTHIOATE HERBICIDE, EPTC, BY RHODOCOCCUS STRAIN JE1 ISOLATED FROM SOIL

Biodegradation of the herbicide EPTC (s-ethyl dipropylcarbamothioate) at greatly enhanced rates, which may lead to poor weed control, can oc cur in soil after successive annual applications. The mechanisms of EP TC degradation by a strain of Rhodococcus sp. (designated JE1) previou sly isolated from soil were evaluated. Degradation of C-14-labeled (at the 1-propyl position) and unlabeled EPTC was followed by thin layer chromatogaphy and gas chromatography-mass spectrometry. The N-depropyl EPTC and EPTC sulfoxide were identified as initial metabolites formed , apparently via hydroxylation of the a-propyl C and oxidation of the S atom of EPTC, respectively. Other products of EPTC degradation ident ified were propionaldehyde, s-ethyl carbonothioic acid, s-methyl carbo nothioic acid, and traces of propylamine. It is proposed that the soil isolate Rhodococcus JE1 degrades EPTC via either an initial hydroxyla tion or sulfoxidation reaction, producing metabolites that can be furt her mineralized to form CO2. The alpha-propyl hydroxylation reaction, however, is thought to be the dominant pathway whereby degradation of EPTC occurs in soil at enhanced rates.