Isolation And Characterization Of β-Cypermethrin Degrading Bacterium

Nineβ-cypermethrin-degrading strains were selected from the contamin-ated soil such as the tea garden where pesticides were often used,by using cypermethrin as carbon source.During 6 days,β-cypermethrin-degrading strains could biodegrade about 60%of substrate(the initial concentration is 100mg/L).All nine strains were rod-shaped,gram-negative bacterium.By 16S rDNA sequence analysis,two of threeβ-cypermethrin-degrading strains were identified as Pseudomonas.sp(the similarity is 98%-99%),the other one was identified as Sinorhizobium.sp(the similarity is 98%-99%).This is the first time to report that Sinorhizobium.sp could degrade cypermethrin.The Sinorhizobium.sp strain was named as CY22-7.3.The rate of strain CY22-7.3 degrading cypermethrin went up from 60%to 80%with extra nutriment.The CY22-7.3 could endureβ-cypermethrin between 200 mg/L to 300 mg/L.The ability to degrade bifenthrin was weak.The good air condition could promote biodegradation of cypermethrin.The optimum degrading pH was about 6.0.Its degrading temperature was much wider.There was no significant difference on degrading rate between 20℃and 30℃The cypermethrin-degrading rate of intracellular enzyme was much higher than that of extracellularβ-cypermethrin-degrading enzyme.It indicted that the cypermethrin-degrading enzyme locates at cell interior.According to the method of detecting plasmid from reported papers,the β-cypermethrin-degrading strain CY22-7.3 has no plasmid.