Biodegradation of Chlorpyrifos and Diazinon Organophosphates by Two Bacteria Isolated from Contaminated Agricultural Soils

The organophosphate insecticides such as chlorpyrifos and diazinon have been widely used to control insects in home, agriculture, and veterinary. These compounds are a threat to public health and the environment; on the other hand, they have low degradation rate and therefore can be stable for a long time in soil. A major factor determining the fate of organophosphate insecticides in soil and water is biodegradation. Two diazinon and chlorpyrifos degrading bacterial strains were isolated from pesticides contaminated soils. The isolated bacterial strains were identified by 16S ribosomal RNA gene and fatty acid methyl ester analysis. Strong correlation was seen between microbial growth and the two organophosphates degradation. On average, bacterial strain 1 and 2 degraded 88.27% and 82.45% of initial applied diazinon in medium and degraded 81.07% and 88.35 % of initial applied chlorpyrifos during 20 days, respectively. The isolated bacterial strains were identified as Acinetobacter and Pseudomonas sp. The highest diazinon degradation were found by Acinetobacter and the highest chlorpyrifos degradation were found by Pseudomonas when cultivated in the mineral salt medium. Discussion and conclusion: The identified pure bacterial strains utilized chlorpyrifos and diazinon as a source of carbon. They were able to degrade most of the parental molecule in 20 days. Therefore, the isolated bacterial strains may have the potential for use in the bioremediation of diazinon and chlorpyrifos-contaminated soils.