Isolation, Screening And Characterization Of Highly Effective Becteria For Degrading Chlorimuron-ethyl

Chlorimuron-theyl has become one of the worst pollutants in soil because of extensive using in the world. As a result, effects of degrading bacteria on chlorimuron-theyl and its bio-degradation has attracted increasing attention. In present research, degrading bacteria were isolated and identified, and its degradation effects were analyzed.One highly effective degrading bacterium of chlorimuron-ethyl named E-1. The E-1 was isolated from soil which has long term applied with chlorimuron-ethyl through enrichment culture method. The E-1 used chlorimuron-theyl as sole nitrogen source. The degradation percentage of chlorimuron-ethyl was 94.74% after cultured 72h in liquid mineral medium containing 10 mg/L chlorimuron-ethyl. Based on the morphological appearances, physiological biochemical characters and 16SrDNA sequence analyse, the E-1 was 100% homologous with Bacillus megaterium. The E-1 was identified as Bacillus megaterium.The E-1 grew fast when the pH value of 5.0～9.0 in beef peptone medium, the E-1 grew best when the pH was 6.0 and stopped grow when the pH value of 10.0. The E-1 grew fast when the temperature was 15～45℃, the E-1 grew best when the temperature was 30℃and stopped grow when the temperature was 50℃. The appropriate aeration was 40～200mL/250mL. The optimum carbon and nitrogen was glucose and yeast powder, respectively.The degrading-enzymes produced by E-1 and located in cells, a kind of inducible enzyme. Temperature and pH were key factors affecting degrading activity of enzymes. The enzymes showed the highest activity at 30℃and pH 7.0 in the Na₂HPO₄-NaH₂PO₄ buffer. The degradation percentage of chlorimuron-ethyl was 52.73% ,when the enzyme content was 4.747 mg/ml andreaction time was 30 min in degradation experiment of chlorimuron-ethyl. The degrading-enzymes were much more stable at pH 6.5～7.0 and 4℃. While the chlorimuron-ethyl initial concentration raised, the degrading activity of enzymes declined; the enzymes degrading activity declined along with the enzymes concentration at the same chlorimuron-ethyl concentration.Bioassay experiment showed that the seeding and height of sensitive crop of degrading bacteria treatment were compatible with the control, on the whole, it considered that E-1 could recover the contamination of chlorimuron-ethyl. The recover effects of E-1 were the most prominent when the chlorimuron-ethyl concentration was 14μg/kg in soil, which the corns'hight inhibition rate of degrading bacteria treatment was 15.66% lower than that of the chlorimuron-ethyl control. The recover ability of E-1 might be even better when the introduction of degrading bacteria was increased.