Identification And Degradation Characteristics Of Chlorimuron-ethyl, Acetochlor And Fomesafen Degradation Bacteria

Chlorimuron-ethyl, acetochlor and fomesafen are three kinds of selective herbicides widely applied for control of weeds in soybeans field, which have been used with an exponential increase as most important herbicide types, due to their special characteristics such as high herbicidal activity, broad action spectrum, good crop selectivity, low toxicity etc. But the knowledge about chlorimuron-ethyl, acetochlor and fomesafen residue on the soil micro-ecological impact and sensitive crop stubble after the injury was still superfieial. Presently, much awareness is created on the environmental pollution problems caused by the pesticide.Many scientists have devoted to study on pesticide residue and metabolism, and microbial degradation of pesticide residues is of particular interest. In this paper, L2 and L6, the strain that were able to degrade chlorimuron-ethyl, was isolated from the soil of long term applied with chlorimuron-ethyl by enrichment culture. Y13, the strain that was able to degrade acetochlor, was isolated from the soil of long term applied with acetochlor by enrichment culture. F12, the strain that was able to degrade fomesafen, was isolated from the soil of long term applied with fomesafen by enrichment culture. Its morphology observation, physiological and biochemical characteristics, 16S rDNA sequence analysis, and biologic actions in environment were studied. The main objective of this paper is to find dominant strain with efficient degrading ability and provide theoretic basis for the practical application of the isolate. The main results are as follows:By the morphology observation, physiological and biochemical characteristics, comparison of its 16S rDNA and phylogenesis tree analysis, the strain L2 was identified preliminarily as Klebsiella sp.; the strain L6 was identified preliminarily as Pseudomonas putida.; the strain Y13 was identified preliminarily as Klebsiella sp.; the strain F12 was identified preliminarily as Klebsiella sp.. The strain L2 16S rDNA partial sequence was deposited in the GenBank database under the accession number DQ831003.The strain L6 16S rDNA partial sequence was deposited in the GenBank database under the accession number EU439424.The strain F12 16S rDNA partial sequence was deposited in the GenBank database under the accession number EU545402. The strain Y13 16S rDNA partial sequence was deposited in the GenBank database under the accession number AB353046.By using UV, the growth were detected respectely and the effects of incubating time, temperature, pH value, inoculation and pesticides concentration on the strains were also studied. The results suggested: The optimal conditions for the strain L2 growth was culture temperature 35℃, initial concentration of chlorimuron-ethyl 100 mg/L, inoculation amount of 5%, pH 7.0. The strain L6 growth was culture temperature 30℃, initial concentration of chlorimuron-ethyl 200 mg/L, inoculation amount of 10%, pH 7.0. The strain F12 growth was culture temperature 35℃, initial concentration of Fomesafen 100 mg/L, inoculation amount of 12%, pH 6.0. The strain Y13 growth was culture temperature 35℃, initial concentration of chlorimuron-ethyl 50 mg/L, inoculation amount of 10%, pH 6.0.The degrading ability of the pure culture was investigated by HPLC.Under the condition of 35℃and pH 7.0, inoculation amount of 5%, initial concentration of chlorimuron-ethyl 100 mg/L, the degrading efficiency of strain L2 could reach more than 80% after3 days. Under the condition of 30℃and pH8.0, inoculation amount of 10%, initial concentration of chlorimuron-ethyl 200 mg/L, the degrading efficiency of strain L6 could reach more than 80% after4 days. Under the condition of 35℃and pH 6.0, inoculation amount of 12%, initial concentration of fomesafen 100 mg/L the degrading efficiency of strain F12 could reach more than 80% after 4 days. Under the condition of 35℃and pH 6.0, inoculation amount of 10%, initial concentration of acetochlor 50 mg/L the degrading efficiency of strain Y13 could reach more than 70% after 5 days.