The intensive use of the insecticides resulted in dangerous effects on environmental components. This study aimed to evaluate the role of bacteria isolated from soil on the degradation of malathion and cyfluthrin. In this study, 230 isolates were obtained from various sources of Egyptian soil contaminated with pesticides. On a solid medium, the isolates were grown with 100 ppm malathion and cyfluthrin insecticides. Thirty-nine bacterial isolates tolerated the tested pesticides, and thirteen grew rapidly. The thirteen isolates were grown in a broth medium with the tested insecticide. According to optical density, six isolates had high density (high growth). Three isolates with the codes S.MC.2, S.MC.12, and S.MC.16 were chosen for malathion degradation, and three isolates with the codes S.M3+M3, S.MC.6, and S.Z.14 were chosen for cyfluthrin degradation. The selected isolates appeared to be able to tolerate high concentrations of malathion (855 & 1425 ppm) and cyfluthrin (400 & 800 ppm). Compared with control, the most efficient isolates were S.MC.16 and S.M3+M3, which had the lowest percentage of cell dry weight reduction after growing in the presence of the above-mentioned insecticide concentrations compared to control.
Keywords: Bacterial isolates, bacteria, malathion, cyfluthrin, biodegradation.