Isolation, characterization and identification of pesticide tolerating bacteria from garden soil

Pesticides are the substances intended for preventi ng, destroying, repelling any pest. Due to bulk han dling or accidental release, they are accumulated in soil wh ich leads to occasional entry into ecosystems that show lethal effects on living systems. In order to overcome the problem of commonly found pesticides namely Endosu lfan, Chlorpyrifos and Cypermethrin. An enrichment cultur e technique was used to isolate bacterial strains fgarden soil tolerating high concentrations of the selected pesticides. Five pure bacterial cultures, named EC 1, EC2, EC3, EC4 and EC5 were isolated and subsequently characte rized by 16S rRNA gene sequencing and biochemical t ests. The optimum temperature, pH and NaCl concentration was determined for them. Growth curve experiments s howed that the bacterial isolates were able to grow in me dium containing the individual pesticide as the car bon source. Tolerance to high levels of metal salts (Co 2+ , Ni 2+ , Cr 3+ , Cu 2+ and Mn 2+ ) and multiple antibiotic resistance was seen in all five bacterial isolates indicating a positive correlation between pesticide degradation and tol erance to metals and antibiotics. By miniprep method of plasmid DNA isolation it was found out that 3 isolates (EC3, EC 4 and EC5) showed presence of plasmid DNA indicating that the resistant trait observed was plasmid borne. Further by transformation of the plasmid DNA from EC3, EC4 and EC5 to Escherichia coli DH5α strain, it was found that the transformed strain acquired the ability to grow in presence of higher concentrations of pesticides. Th us such findings may be useful in designing a multi resista nt bacterium that can be used to return the altered environment to its original condition.