| Chlorpyrifos is a broad-spectrum,chlorinated and organophosphate insecticide,acaricide,widely used as pest control over a variety of crops,lawns and ornamental plants.Repeated use of chlorpyrifos not only changes the soil microbial community structure,but also poses a potential health risk to other non-target organisms such as mammals.Based on the highly effecient degrading strain Cupriavidus nantongensis X1,we used electrical and chemical transformation methods that leading plasmid pTR102?containing gene luxAB?into the chlorpyrifos-degrading strain X1,therefore the labeled strain Lux-X1 was obtained.The aim of this study was first to explore the colonization of the Lux-X1 in soil,also to study the effect of the humidity and the concentration of chlorpyrifos on the migration of Lux-X1,finally was to investigate the activity that strain Lux-X1 and the original strain X1degrade chlorpyrifos and TCP.The specific results are as follows:1.Trying with different combinations of electrical conversion parameters,different plasmid concentrations,finally we found that plasmid pTR102::LuxAB was successfully introduced into the chlorpyrifos-resistant strain X1 under 25?F capacitance,2.5 kV field strength,200?resistance,and 1525.3 ng·?L-1DNA concentration.After obtained,the labeled strain Lux-X1 were seeded on the non-resistant solid medium plates 15 times consecutively,cultured in the liquid culture medium and then inoculated into the soil.After60 days,Lux-X1 remained steady light.2.The degradation activity of strain Lux-X1 and X1 degrade chlorpyrifos and TCP was investigated in different media?soil and water?.The results showed that,when the labeled strain Lux-X1 was put into soil for 10 days,the degradation rates of 50,100 and200?g·g-11 chlorpyrifos were 85.4%,70.5%and 57.6%,respectively,it could also degrade72.3%of TCP when the initial concentration is 20?g·g-1,Likewise,when putting into the original strain X1,the degradation rates were 92.2%,82.4%and 51.6%,also,strain X1could degrade 85.0%of TCP.Cultured in water with 200?g·mL-11 chlorpyrifos or 20?g·mL-1 TCP for 24 h,Lux-X1 could degrade 70.6%of chlorpyrifos and 99.9%of TCP,for the original strain X1,it degraded 62.6%of chlorpyrifos and 99.8%of TCP instead.Either the labeled strain Lux-X1 or the original strain X1 had no degrading activity against high concentrations of TCP(50?g·g-1).3.Studying different humidity afftected the colonization of labeled strain Lux-X1 in soil,we found that the viability status was 100%WHC>80%WHC>60%WHC>40%WHC within 6 days.Although the number of the strain in each group was close to each other,number of viable bacteria was significantly lower than that of the other three groups when the water content was 40%WHC,proving that low humidity inhibited its growth to some extent.4.The longitudinal migration of the labeled strain in soil was studied by measuring the number of strains from the soil in the PVC columns and in soil columns?simulating natural circumstance?at different depths.Different treated soil affected the longitudinal migration of the labeled strain as the migration rate of the soil with 100%WHC was higher than that with 60%WHC.However,the number of strain was significantly higher from the column with chlorpyrifos than the column without,even with the same water content 60%WHC)and sampling at the same time.The results of the soil columns experiment showed that the labeled strain Lux-X1 can migrate down to 30 cm soil depth at 10 days and migrate to 40 cm,the bottom of the soil discs at 15 days.The number of strains was significantly higher in groups with chlorpyrifos than that of the groups without,which was consistent with the column.5.Adding strain Lux-X1 to the soil respectively,we compared the degradation performance of the labeled strain Lux-X1 with the original strain X1 after 30 and 60 days of colonization in soil column.The results showed that under the same background concentration of 100?g·mL-1,cultured for the same 24 h,the degradation rates of the labelled strain Lux-X1 and the original strain X1 to chlorpyrifos were 77%and 78.6%,and69.1%and 72.8%after 60 says of colonization.Moreover,it was indicated that the recovered labeled strain had stable biodegradability to degradate chlorpyrifos during colonization by comparison. |
PDF Full Text Request