Determination of organochlorine pesticides in agricultural soil with special reference to gamma-HCH degradation by Pseudomonas strains

Soil samples were taken from different agricultural fields and analyzed for organochlorine pesticide residues by gas chromatography. The analysis indicated that the soil samples contained some common organochlorine pesticides DDT, DDD, DDE, HCH and Aldrin. gamma-HCH was detected as 47.35 ppb whereas the concentrations of alpha-HCH, beta-HCH, p('),p(')-DDE, o('),p(')-DDT were 38.81, 1.79, 7.10 and 13.30 ppb, respectively, in the same soil. Two Pseudomonas strains isolated from agricultural soil were found to possess gamma-hexachlorocyclohexane degrading ability when the isolates were grown in a mineral salt medium containing gamma-HCH as the sole source of carbon and a number of metabolites were produced and detected by the gas chromatography. These bacterial isolates were further tested for carbohydrate and amino acid utilization as well as for their susceptibility against 10 commonly used antibiotics namely amoxycillin, chloramphenicol, cloxacillin, doxycycline, methicillin, nalidixic acid, neomycin, nitrofurantoin, streptomycin and tetracycline. Both the isolates were also screened for plasmid DNA and found to harbour a single plasmid.