Screening And Degrading Effect Evaluation Of Pendimethalin-degrading Bacterium

Pendimethalin is a dinitroaniline selective soil treatment herbicide widely used in cotton field in Xinjiang.A large number of investment of pendimethalin severely damaged the soil microorganisms and influenced the soil quality.The study utilized the microorganism diversity in soil to directly screen the efficient strains of degrading pendimethalin by enr ichment culture method from Xinjiang f ield and discussed the degradation characteristics,conditions and efficiency to provide a basis for bioremediation of pendimethalin-contaminated environment.1.The efficient strains of degrading pendimethalin were screened out by enrichment culture method from Xinjiang f ield soil,9 strains of bacterial strains with high tolerance and degradation ability were screened by plate method,and the degradation abilities of them were determined by high performance gas chromatography.The results showed that there were 2 strains of highly effective degrading bacteria named JY-2 and JY-5,two strains in culture fluid can degrade more than 70% of 200 mg/L pendimethalin after 3 days and degrade more than 90% of 500 mg/L pendimethalin after 9 days.2.Identification of bacterial strains were completed with morphological analysis and comparison sequences of 16 S r DNA and phylogenetic anlaysis.Bacterial strains of JY-2 and JY-5 were Serratia sp.and Pseudomonas sp.,respectively.3.The degradation conditions of the strain were studied in the culture medium.The results showed that the strains could utilize carbendazim as sole carbon source for growth and at carbon source concentration 0.5%,inoculum 10%,pendimethalin 200 mg/L,pH 7.0 and temperature 30? culture conditions,the pendimethalin degradation rates of the two strains can respectively reach 83.34% and 82.79%.4.JY-2 and JY-5 were taken as the tested strains to study the influencing factors of pendimethalin reparation in soil microcosms.The results showed that the degradation rates of bacterium for 200 mg/kg pendimethalin after 15 days were 66.18% and 65.66% with 0.6×109 cfu·g-1 inoculation quantity.The degradation rate was low if the inoculation quantity was less than this concentration;The effects of soil temperature and moisture on the degradation rates were obvious,the most suitable temperature was 30? and optimum humidity was 600 g/kg.5.The biological method was used to verify the degradation effects of strains.When treated with pendimethalin,the seedling emergence rates of maize and cotton were 33.33% and 71.11% respectively,after adding degrading bacterium,the pendimethalin concentration reduced in soil,the seedling emergence rates of maize increased to 55.56% and 67.78%,the seedling emergence rates of cotton increased to 88.89% and 91.11%,there were signif icant differences.Inoculation of bacterium JY-2 and J Y-5 can reduce the growth inhibition of maize and cotton in soil in different degrees,which had a certain degree of soil remediation.