RING HYDROXYLATION OF N-METHYLCARBAMATE INSECTICIDES BY RHODOCOCCUS TE1

Rhodococcus TE1, a soil bacterial isolate shown previously to metabolize several thiocarbamate herbicides, organophosphorus insecticides, and s-triazine herbicides, was found to degrade carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methylcarbamate), propoxur (2-isopropoxyphenyl methylcarbamate), and carbaryl (l-naphthyl methylcarbamate) in a defined growth medium. The insecticides were cometabolized, serving neither as a carbon nor as a nitrogen source for growth. Oxygen was required for metabolism of the insecticides. Carbofuran, carbaryl, and propoxur were each converted to hydrophilic end-products 16 mass units larger in size than the respective parent compounds. On the basis of NMR and GC-MS analysis, the end-product of carbofuran metabolism was identified as 5-hydroxycarbofuran. Hydroxylation of the aryl N-methylcarbamate insecticides was associated with a 77 kb plasmid whose loss resulted in the inability to metabolize these compounds. Given the ubiquity of the rhodococci in soils, and the variety of pesticides degraded by strain TE1, it is likely that these Gram-positive bacteria contribute significantly to the dissipation of pesticides in the environment.