Analysis of the degradation characteristics of organophosphorus pesticides by different strains of Bacillus cereus

A feasible way to remediate organophosphorus pesticides contaminated water and soil environment is to screen degrading microorganisms because of its important significance in the biodegradation of pesticide residue.The degrading bacteria were isolated from the wastewater treatment system of the pesticide enterprises by the method of enrichment culturing and analyzing the residue of organophosphorus pesticides at the definite time.The traditional morphology,physiological-biochemical properties as well as 16S rDNA gene sequence analysis were applied to the bacteria classification.Simultaneously,the degrading characteristics of methyl-parathion,chlorpyrifos and triazophos by the bacteria were also studied.The results indicated that 10 bacteria with the ability of degrading methyl-parathion and chlorpyrifos were separated from the liquid enriched culture and HY-1,HY-2 and HY-4 strain were determined as the research object.The three strains were identified as different strains of Bacillus cereus and the Genbank registration numbers were eu915687,eu915686 and eu915688,respectively.The degradation rates of HY-1,HY-2 and HY-4 reached 91.7%,87.7% and 92.4% within 72 h when the medium contained 50 mg·L 1 of methyl-parathion and the degradation rates among three strains had no significant difference at 0.05 level.When the concentration of methyl-parathion was 100 mg·L 1,the degradation rates declined and the degradation rate by HY-2 dropped by 23% and had significant difference with the other two strains.When the concentration of chlorpyrifos were 100 mg·L 1,the degradation rates of HY-1,HY-2 and HY-4 reached 64.8%,53.7% and 56.5% within 72 h,respectively.There was no significant difference in the degradation rate when the concentration of chlorpyrifos ranged from 50 mg·L 1 to 200 mg·L 1 by HY-1 and HY-4,HY-2 had significant difference with HY-1 and HY-4 at the 0.05 level.The degradation efficiency of 100 mg·L 1 triazophos by three strains was weak,HY-2 reached the highest and was only 20.7%.The degradation rates by the other two strains were lower and had no significant difference at the 0.05 level.The results reflected the diversity of the degradation characteristics of organophosphorus pesticides by different Bacillus cereus strains.