Long Residual Effect Of The Herbicide Chlorimuron-ethyl Degrading Bacteria Identification And Degradation Characteristics

Chlorimuron-ethyl is a broad-spectrum, highly effective sulfonylurea herbici-des, which is widely used in the soybean field, it can highly selective Control sedges, broad-leaved weeds and some grass weeds, so it has been widely applied in China. However, because of its long residual, easily caused the agriculturalenvironment pollution, serious sensitive crop phytotoxicity, it has become important issues facing the agricultural production.Biodegradation is an important way of the chlorimuron-ethyl decomposition in the environment, this study was to obtain the chlorimuron-ethyl degrading microorganisms, and study their chlorimuron-ethyl degradation characteristics, which will provide a theoretical basis for the biological treatment of chlorimuron-ethyl contaminated water, insitu biological revise of the environment polluted by chlorimuron-ethyl . Specific work was done as follows:In this study, we use liquid mineral salts medium plate enrichment culture and direct separation method, screened an efficient degrading bacteria using chlorimuron-ethyl as a sole carbon source named T9DB-01 (GenBank Aeeession No. GU395783), which can degrade 92.1% of chlorimuron-ethyl after 5 days using liquid chromatography detection. Bioassay validation obtained on the degradation rate show that strain T9DB-01 can make the rice root length restored to near control levels. Molecular identification results show that the Similarity of 16S rDNA genesequences of strain T9DB-01 and Pseudomonas sp. is 100%, combined with theresults of the optical microscopy, scanning electron microscopic morphology andphysiological biochemical characterization infer that the strain is Pseudomonas sp.We studied basic law of the identified bacteria Pseudomonas sp.growth and degradation of chlorimuron-ethyl. Inoculated in basal medium, at the time of 0～32h the strain T9DB-01 was in the delay period, 32～64h in the logarithmicphase, after 64h into the stable and decline phase. The chlorimuron-ethyl concentration and bacteria growth changes was in the same trends. Strai-n T9DB-01 used chlorimuron-ethyl, nicosulfuron easier than atrazine, imazethapyrand fomesafen. The optimal carbon source was maltose and sodium citrate, and the optimal nitro-gen source was tryptone, ammonium nitrate and ammonium sulfate.The expermiment also studied the environmental factors affected Pseudomonas sp. growth and degradation rate. Univariate results showed that best pH was 7.0 for the strain degradation of chlorimuron-ethyl, optimal temperature and liquid volume was 30℃and 100/250mL respectively, the best inoculum size was around 4%, optimal growth concentration was 300mg/L. Cell growth and chlorimuron-ethyl degradation rate was in the same trend.Orthogonal test studied the pH value, temperature, liquid volume, inoculum size and concentration on the degradation of chlorimuron-ethyl by strain T9DB-01. The optimal combination is A2B2C3D2E2, the inoculum was 4%, pH value of 8.0, the temperature of 30℃, liquid volume of 100mL/250mL, the concentrationof 200mg/L.The degradation rate of strain T9DB-01 is 95.7% in 5 days in this condition.