Screening And Identification Of Chlorpyrifos And Atrazine Degrading Bacteria

Chlorpyrifos and atrazine are two common chemical pesticides.They are widely used due to their high efficiency,low cost and long duration of efficacy,but their long-term use can pollute soil and water bodies,destroying the ecological balance and threatening human he alth.Traditional pesticide degradation mainly relies on physical and chemical methods,but th eir efficiency is low,the investment is large and it is easy to cause secondary pollution.Micro bial remediation techniques are an important means of pesticide degradation due to their high efficiency,safety and environmental friendliness.In this experiment,chlorpyrifos and atrazine were used as experimental objects.Pesticide-degrading bacteria were isolated and screened from three samples: agricultural soil,sludge from aeration ponds of wastewater treatment plan ts and soil from pesticide plant outfalls.The results of the study are as follows.1.The enrichment and domestication methods were used to screen for degrading bacteria from the three samples.The results showed that a total of 27 strains were obtained,including9 chlorpyrifos degrading bacteria and 10 atrazine degrading bacteria from the domestication method.Seven strains of chlorpyrifos degrading bacteria and four strains of atrazine degradin g bacteria were obtained by enrichment(three strains could degrade both chlorpyrifos and at razine).2.The degradation rates of the strains were measured using high performance liquid chro matography.The results showed that the degradation rates of 16 chlorpyrifos-degrading bacteria ranged from 18.09% to 76.44% at 37 ? and p H 8 for 12 h.The degradation rates of14 atrazine degrading bacteria ranged from 29.73% to 68.37% at 37 ? and p H 8 for 12 h for100 mg/L of chlorpyrifos,with 9 strains having a degradation rate of more than 50%.The degradation rate of 100mg/L atrazine ranged from 29.73% to 68.37% after 12 h at 37 ? and p H 8.Three strains degraded more than 50%.3.The degrading bacteria with the highest degradation rates for chlorpyrifos and atrazine were selected for identification.The results showed that the A3 strain had the highest degradat ion capacity of 76.44% among the chlorpyrifos-degrading bacteria,and that the bacteria were able to grow on chlorpyrifos as the only carbon source.Among the atrazine degrading bacteri a obtained,strain B3 had the highest degradation capacity of 68.37%.The degrading bacteriu m B3 was also able to degrade chlorpyrifos.Morphological observations,physiological and bi ochemical tests and 16 S r RNA gene sequencing were carried out to identify A3 and B3 as Bur kholderia sp.4.The effect of different p H,temperature and inoculum on the degradation rate of degrad ation bacteria A3 and B3 was determined.The results showed that the degradation rates of Ba cteroides A3 and B3 were the lowest at 18 ? and the highest at 36 ?.The degradation rate o f degradation bacteria A3 was the lowest at p H 5 and the highest at p H 8.The degradation rate of degradation bacteria B3 was the lowest at p H 5 and the highest at p H 7.The inoculation ra te had a small effect on the degradation rate of A3 and B3,with the lowest degradation rate at1% and the highest degradation rate at 4% inoculation,and the lowest degradation rate at 1%and the highest degradation rate at 3% inoculation for B3.5.The effects of different p H values and temperatures on the growth of degrading bacteri a A3 and B3 were determined.The results showed that the growth of degradation bacteria A3 and B3 was best at temperatures between 30 ? and 36 ?,and the growth of degradation bact eria A3 and B3 was best at p H values of 6-9.6.The optimum fermentation conditions were optimised for strain B3,which can degrade both chlorpyrifos and atrazine.The results showed that the best growth of B3 was achieved at a temperature of 36 °C,a p H of 8 and an inoculum level of 3%,with a degradation rate of 86.73% for chlorpyrifos and 76.19% for atrazine.