Abstract

he use of pesticides is very critical in protecting the farmers’ investment in seeds, fertilizer and labour since they provide a sure cover from damage by pests. The use of pesticides is therefore inevitable and the environmental pollution due to pesticides and their residues will continue to be a challenge. In this study, bacterial strains capable of degrading methomyl (S-methyl-N-[(methylcarbamoyl) oxy]-thioacetimidate) and carbofuran (2, 3-dihydro-2, 2-dimethyl-7-benzofuranyl methylcarbamate) were isolated from soils sampled from horticultural farms with a history of pesticide usage. High pressure liquid chromatography was used to monitor biodegradation of both methomyl and carbofuran using reference standards and acetonitrile and water as mobile phases. Partial 16S rDNA sequence analysis indicated that the carbofuran-degrading strains were closely related to members of the genus Pseudomonas and Alcaligenes while the methomyl degrading strains were closely related to members of the genus Flavobacterium and Alcaligenes. The morphological and biochemical characteristics of the isolates also confirmed the phylogenetic signature. The study established that the activities of the esterase and phosphatase enzymes correlated well with biodegradative capability and recommends possible application of the isolates in the in vivo bioremediation of pesticide contaminated soils.

Key words: Pesticides, carbofuran, methomyl, biodegradation, bacteria