Isolation, Identification And LuxAB-labeling Of Chlorpyrifos Degrading Strain Sphingopyxis Terrae R17

1. 24 strains were isolated from the sludge and soil of pesicide factory through shaking culture and soil enrichment method, among whcih six strain have better degrading efficiency of chlorpyrifos that are named as E30, R17, P5, B1, Z5, T15and the degrading rate were55.47%,32.27%,58.15%。34.76%,27.10%,42.01% respectively in 2d.2. By the method of tri-parental mating, the marker gene luxAB was successfully transferred into R17 strain, and a marked strain, LuxR17, was successfully obtained. The plasmid with luxAB did not lose after 20 transfers, and the strain was genetically stable.3. Strain R17 was identified preliminarily as Sphingopyxis terrae based on its physiological and biochemical characters and its 16 S rDNA homologue sequence analysis.4. Under the optimal growth condition, 35℃and pH 7-8, Strain R17 could reach 9.18×10⁸ cfu-mL^-1 after 28h and LuxR17 strain reach 1.04×10⁹ cfu-mL^-1 after 32h.5. The chlorpyrifos degradation characteristics of R17 strain and LuxR17 strain were studied at different times under the initial concentration of 10 mg-L^-1. The results showed that the degradation rate of chlorpyrifos by strain R17 with the inoculation of 9.18×10⁷ cfu-mL^-1 were18.59%, 31.23%, 36.55% and 47.69%, and that by LuxR17 with the inoculation of 1.04×10⁸ cfu-mL^-1 were 17.72%, 24.14%, 35.06% and 48.48% respectively in 1d, 2d, 3d and 4d.6. The chlorpyrifos degradation characteristics of R17 strain and LuxR17 strain were studied with different initial chlorpyrifos. The results showed that with initial concentration of 1 mg-L^-1, 5 mg-L^-1, 10 mg-L^-1, the chlorpyrifos degradation rate by R17 strain reached 50.21%, 43.46% and 31.23% and that by LuxR17 strain reached 41.64%, 35.20% and 24.14% after 2d respectively.7. Experiments were conducted to investigate the distribution of LuxR17 strain in different soil. The results showed that the trends of LuxR17 strain in different treatments of soils were generally declined, but the dicline speeds were different in different treatments of soils. The cell number of LuxR17 strain in sterilized soil was higher than that in non-sterilized soils and the cell number in soil with chlorpyrifos was higher than that in soil without chlorpyrifos.8. Biodegradation kinetics of chlorpyrifos in different treatments of soil was studied. The results showed that the degradation rate of chlorpyrifos in no-sterilized soil was higher than that in sterilized soils and the degradation rate in soil with LuxR17 strain was obviously higher than that in soil without LuxR17strain. With initial concentration of 20 mg-L^-1 chlorpyrifos, the degradation rates of chlorpyrifos by LuxR17 strain were 55.92%, 72.27%, 89.13% and 98.31% in no-sterilized soil and were 42.37%, 70.92%, 80.04% and 94.70% in sterilized soil respectively in 3d, 6d, 9d and 12d.