Isolation, Identification And Characterization Of An Imazethapyr-degrading Strain

Imazethapyr, a kind of imidazolinone herbicides developed early and applied widely in our country, is one herbcide with the trait of broad-spectrum, high efficiency, low cost, and low dosage, and it becomes a powerful chemical for production of soybean. However, serious phytotoxicity to sensitive crops caused by imazethapyr such as long-term residual effect, is affecting on agricultural production severely. Microbial degradation and remediation is a new approach occurring rencently. In this research, residual problems caused by imazethapyr was focused on, high efficiency imazethapyr-degrading strains were sreened via the high pressure enrichment method from abundant soil microbial resources in China, and the biological characteristics, bio-degrability, bioremediation of imazethapyr of the strain were investigated respectively. The main results are following:1. One strain of imazethapyr-degraded bacterium named P14 was isolated from the sludge of imazethapyr production factory via the high pressure enrichment method in this study. Classification was determined by the analysis of morphological, physiological and biochemical characters and sequencing of 16S rDNA for P14 strain respectively. Simultaneously, degradation performance was investigated preliminary. The results indicated that P14 strain was identified as Shewanella decolorationis.2. Strain P14 growed quickly in LB medium, this strain could grow from pH 5.0-9.0 and temperature at 28-37℃. The strain P14 increased when the ventilation was increased, it indicated P14 was an aerobiotic strain. The best loading capacity was 25 mL/250mL. In basical medium, the optimal carbon source and nitrogen source for the strain growth is sucrose and yeast extract; the best proportion is 1:3.The optimal parameters for P14 strain to degrade 100 mg/1 imazethapyr up to 91.96% within 72 h were at 30℃, pH 6.0, inoculated by 7% in mineral salt medium, the rediual concentration of imazethapyr imazethapyr was 5.88 mg/l. P14 was also able to degrade some other imidazolinone herbicides, e.g. imazamethabenz-methyl, imazaquin and imazamox, at 30℃, inoculated by 7%,220r/min condition with degradation efficiency of 25.39%,16.83% and 33.26% respectively. The imazethapyr -degrading metabolite by strain P14 is N-(hydrazinecarbonyl)-2-(iminomethyl)-4- methyl-5-oxo-4,5- dihydro-l-H-imidazole-4-carboxamide.3. The bioassay result showed that strain P14 degraded imazethapyr in the soil significantly in greenhouse, the crops could grow normally after remediated by P14 strain in the pots. The P14 could degraded imazethapyr efficaciously with concentration of 100 mg/1 in the pots. Local native microorganism did not affect degrability of P14, indicating P14 being strong adaptability in the soil. These results are providing a valuable reference for application in the field.