Evaluation of diazinon pesticide biodegradation efficiency by native bacterial strains isolated from contaminated soils in agricultural areas

BACKGROUND AND ABJECTIVEDiazinon is one of the most widely used organophosphorus pesticides in agriculture. The accumulation of this pesticide in agricultural soils and its intrusion into water sources pose a risk to public health and the environment. The aim of this study was to investigate the efficiency of bioremediation of diazinon pesticides by indigenous bacteria isolated from contaminated soils.MATERIALS AND METHODSSoil samples were collected from a tomato greenhouse in Meybod city. The soil samples were cultured in a mineral nutrient medium containing ۱۰% (v/v) diazinon as the sole carbon source. In order to adapt the isolates to higher concentrations, culture media containing ۲۰-۷۰% diazinon were used in the next experiments. The growth rate of the isolates was determined by measuring the optical density of the samples with a spectrophotometer at a wavelength of ۶۲۰ nm. The synergistic effect of the isolates in the biodegradation of diazinon was also investigated. Superior isolates were identified by biochemical and polymerase chain reaction (PCR) assays. The amount of the pesticide diazinon remaining in the culture medium was measured by gas chromatography (GC) with flame ionization detector (FID).RESULTS AND DISCUSSIONCulture of the isolates showed that there were two superior isolates in the soil samples that could grow in a saline medium containing ۶۰% (v/v) diazinon. The results of biochemical tests and partial ۱۶SrRNA gene sequence analysis and blast showed that the two best strains belonged to Pseudomonas aeruginosa and Entrobacter huaxiensis with ۹۴.۵% and ۹۴.۷% similarity, respectively. The results of GC analysis showed that Ps. aeruginosa and E. huaxiensis were able to degrade ۸۷.۴۵% and ۷۵.۰۴% of diazinon, respectively. Simultaneous cultivation of these two species in the culture medium containing diazinon showed no synergistic effect and resulted in the degradation of only ۴۴.۳۴% of diazinon.CONCLUSIONThe species of Ps. aeruginosa and E. huaxiensis are suitable candidates for the biodegradation of diazinon in contaminated soils. Biodegradation efficiency decreases in the presence of both bacteria, probably due to the release of secondary metabolites. In order to increase the biodegradation efficiency of diazinon, physical and photocatalytic solutions can be considered along with the use of bacteria.

کلیدواژه ها:

Biodegradation ، Diazinon ، Pesticide ، Pseudomonas aeruginosa ، Entrobacter huaxiensis