Imidazolinone Herbicides Degrading Bacteria Isolation, Identification And Degradation Characteristics

Imazethapyr and Imazamox, the imidazolinone herbicide, are widely used in soil for their efficient weeding effect. After long time used, the residues increased year after year, and seriously inhibit the following crops growth. Herbicide are degraded by some microorganism in soil. Eeffects of degrading microorganism on imidazolinone herbicide and its bio-degradation has attracted increasing attention.In present research, degrading bacteria and fungus were isolated and identified, and its degradation effects were analyzed. We found 23 strains baceteria and fungus which can degradate imazethapyr and imazamox, named IB1-8, FB1-5, HB1-5 and HF1-4. The degradation percentage of Imazethapyr and Imazamox is from 9.36% to 92.46% after cultured in liquid mineral medium by HPLC.Based on the morphological appearances and physiological biochemical characters, the degrading bacteria IB1 and IB2 belong to Agrobacterium, IB3 and HB2 belong to Brevibacteriu, IBS belong to Acinetobacter, IB6 and IB7 belong to Corynebacterium; HBland HB3 belong to Pseudomonas, HB4 belong to Micrococcus, HB5 belong to Stroptococcus, IF1, IF4 and HF1 belong to Aspergillus, IF2, IF3, IF6 and HF2 belong to Penicillitm, IF5 belong to Trichoderma, HF3 belong to Mucor, HF4 belong to Rhizopus.Highly effective degrading bacterium of Imazamox grew fast in inorganic salt culture medium,0-6h in the lag phase,7-17h in the exponential growth phase, and end in 18h then go into a stationary phase. The degrading bacterium grew fast when the temperature was 25-40℃, degrading bacterium grew best when the temperature was 37℃.when the pH value of 5.0-9.0, the degrading bacterium can grew and grew best is when the pH was7.0. Under optimum conditions, determination of the degradation efficiency was found to increase with the number of bacteria, residual herbicide in the culture medium was gradually reduced, after 48h cultivating in culture medium, the concentration from 800mg/L reduced to 60.32mg/L, degradation efficiency of 92.46%, with higher degradation efficiency. The fragment of the degradation gene of imazamox was be cloned from the highly effective bacteria IB5. The mutants were made by Tn5 transposon vector pSZ21, and we got 418 strains with the degradation of defective strains. To defective DNA as template, we cloned a 1267bp length sequence by TAILPCR. Analysis it. we found that it is highly homologous with the diphenol oxidase of Cryptococus neoformans. Maybe it is very important to degradate imazamox.