Optimization of Growth Response Parameters, Screening and Molecular Detection of Pesticide Degradation Genes in Bacterial Isolates from Agricultural Soils

Abstract

Pesticides are organic compounds synthesized and used for pest control. The excessive and continuous dispersion of pesticides in the environment results in environmental pollution, necessitating remediation. This study investigated the potential of bacteria isolated from farmland soils in Kano Metropolis, Kano State, Nigeria, with a history of dichlorvos (2,2-dichlorovinyldimethylphosphate) and carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) application, to biodegrade these pesticides. Three sampling sites were involved in sample collection, and the soil physicochemical parameters from each sample were determined. Isolation, identification, and screening of the bacterial isolates capable of utilizing the pesticides as sole sources of carbon were carried out. The following parameters (concentration of the pesticides, pH, temperature, agitation, and incubation time) were optimized to maximize degradation. The potent bacterial isolates were further subjected to molecular analysis for the detection of opd and mcd genes. The pesticide-degrading bacteria were identified as Bacillus sp., Serratia sp., and Pseudomonas sp. Serratia sp. recorded the highest growth in the presence of 1% v/v dichlorvos, while Pseudomonas sp. exhibited maximum growth at a 1% w/v carbofuran concentration. The optimized conditions that yielded the maximum microbial growth are: 100 mg/L pesticide concentration for Serratia sp. and 300 mg/L for Pseudomonas sp., a pH of 7.0 and an agitation level of 100 rpm for both organisms, a temperature of 35°C for Serratia sp. and 30°C for Pseudomonas sp., and an incubation time of 5 days for both organisms. The opd and mcd genes were identified from Serratia sp. and Pseudomonas sp. respectively. These results suggest that the isolated bacteria have the potential to degrade dichlorvos and carbofuran pesticides from the contaminated soil.