Isolation And Degrading Characterization Of Phorate-Degradation Bacterium

Phorate is the most toxic pesticide in organic phosphorus insecticides, and its toxicity is the highest in organic phosphorus insecticides. Phorate and its more toxic metabolize productions can exist more than one-two months or much longer in plants. Moreover, it can exist in soil for more than fifty days. If it is improper used or used continually for long time, human and environment would be endangered. Therefore, phorate had been forbid to use it on vegetables, fruits and herbal medicines in China. Now, it is mainly used in soil to dispose before seeding corn and to prevent underground insect pests and seedling pests. Phorate is allowed to be used through mixing with certain pesticides as well.In this paper, a phorate degradation strain JZ1 that identified as Ensifer sp. was isolated from phorate contaminated soil, which could degrade phorate stably. Growing in general substrate, it was the period of logarithmic growth after four hours, and 24 hours later, it reached the maximum amount of growth. The strain grew well under pH 5.0-9.0 and the best pH condition was 8.0. The optimum growth temperature for JZ1 was 37℃. The best carbon source and nitrogen source for JZ1 were dextrose and barm paste resperctively. The strain was sensitive to NaCl that it would grow badly in medium containing 8.0% or more NaCl, while the best concentration for the strain was 0.5%.Basing on the fact that JZ1 was effete during experiment, the paper renewed the ability of grow and reproduce by using soil lixivium rejuvenesce. Moreover, its culture and biology characteristics accorded with original strain.The strain could tolerate phorate with a high concentration of 28000mg/L. The degradation rate of 200mg/L phorate for JZ1 was 42.2% after 24 hours at isolating initial stages, and 56.3% after domesticating to 800mg/L. The degradation rate was improved to 67.8% and 83.2% by simply chemical and UV mutations separately. Degradation curve was measured by gas chromatography. The amount of pesticide descended quickly between 12 hours to 24 hours and degradation rate was 83.99% after 24hours. It is the first report about Ensifer sp. microorganism with a great highly phorate-toleration and degradation capability.Basing on bond positions of the effective ingredient of phorate, which were easy to cut, the paper conjectured the degradation process of phorate was:firstly, phorate changed to diethyl phosphoric acid, and then, became phosphoric acid. Parts of phosphorus may be absorbed by JZ1 or synthesized to sertain parts of thalli.At the very beginning, cells of JZ1 were short bacilliform. But they became globate after domestication and remained this modality since then. Moreover, other biological characteristics and degradation capability were changeless all along. In all, the result was that JZ1 had the capability of well generation's stability.