Isolation and Characterization of Novel Bacterial Strain from Egyptian Lakes Capable of Degrading the Widely used Pesticide, Methomyl

Mervat S. Mohamed

Department of Chemistry (Biochemistry Specialty), Faculty of Science, Cairo University, Egypt.

ABSTRACT: The use of microorganisms is expected to be an effective tool for remediation of environments contaminated with various pesticides. We carried out a large scale screening program the aim of which is to isolate certain pesticide degrading bacteria from pesticide contaminated water samples collected from Egyptian lacks. One type of bacterial strain was isolated and identified as Aeromonase hydrophila SM11 using the pesticide methomyl as a sole source of carbon and energy. This strain was capable to degrade the pesticide at a concentration up to 750 mg/l .Also the strain has the ability to utilize pesticide at different temperature and a range of pH. The ability of the bacteria to degrade the pesticide in a liquid culture was confirmed by high performance liquid chromatography (HPLC). A single plasmid approximately 5kb named, pSM11 was isolated from this strain. Our study has shown that neither the repetitive cultivations in nutrient medium without pesticide for 20 days successive nor the treatment with mitomycin C has lead to loss of the plasmid or the phenotype. These findings might indicate that the plasmid and the phenotypic expression of methomyl degradative genes are quite stable. This however has not shed any light on whether the gene(s) encoded the pesticide degrading enzyme are plasmid or chromosomal encoded. The results of our study suggest that the isolated strain is a valuable bacteria for degradation of methomyl under adverse environmental conditions and may be used for the detoxification of methomyl in water as well as in contaminated soils.

KEYWORDS: Curing, Degradation, Methomyl, Phenotype Stability, Plasmid

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