Degradation Characteristics, Functional Location Of A Bacterial Strain Bacillus Latersprorus DSP Degrading Chlorpyrifos And Its Possible Application In Bioaugmentation

Chlorpyrifos is an organophosphorus insecticide with widely used, numerous investigations were reported on biodegrade of chlorpyrifos. However, little information is available in the literature on degradative plasmid for chlorpyrifos degradation and its possible application in bioaugementation.A bacterial strain DSP capable of degrading chlorpyrifos was isolated, and the degradative kinetics and the possible degradation products were measured in this study. The function of the isolated strain DSP was located on a plasmid, and the possibility of using using the degradative plasmid to enhance chlorpyrifos degradation in soil was investigated.The results are shown as follows:Based on its physiological and morphological characteristics, the isolated strain was identified as Bacillus Latersprorus. The ability of the isolated strain DSP to chlorpyrifos depends on pH, temperature and concentration of chlorpyrifos.The half-lives of chlorpyrifos at concentrations of 1 and 10mg·L^-1 were measured to be 1.48 d and 5.00 d, respectively. However, it was inhibited significantly by high concentration of chlorpyrifos. The degradation rate of chlorpyrifos by the strain DSP was affected by pH and temperature following an order of pH7.0>pH 5.0>pH 9.0, and of 35℃>25℃>15℃, respectively.TCP was dermined and identified as a main degradation products of chlorpyrifos by No accumulation of TCP was aobserved, it was likely that TCP was further transferred to be TMP. According to the capability of the strain DSP to utilize chlorpyrifos as sole carbon and energy sources, it is reasonable to propose that chlorpyrifos is mineralized by the bacterial strain.A plasmid with a size of approximately 20kb was found in Strain DSP. The strain lost its ability to degrade chlorpyrifos when the plasmid was removed by acridine orange and heating. When the plasmid was transferred into Escherichia coli JM109 and back into plasmid-removed DSP the transformants obtained the ability to degrade chlorpyrifos. These observations indicated that the plasmid of strain DSP is responsible for the degradation of chlorpyrifos.Strain DSP, Escherichia coli JM109 containing pDOC, soil bacterial suspention , andpDOC were inoculated into soil. After repeated addition of chlorpyrifos , the degrading rate of chlorpyriofs itself in soil treated with with pDOC was enhanced gradually, and the number of microbes degrading bacteria was increased simultaneity. It could be concluded that the plasmid pDOC was transfer into soil microorganisms, and thus enhancing the degradation of Chlorpyrifos in soil.Compared to the treatments without CaCl2, degradation of Chlorpyrifos in soil was fastened by the addition of CaCl2 , and the nember of microbes degrading chlorpyrifos was also more enhanced.The results obtained in this study indicated that the degradation of chlorpyrifos by the isolated strain DSP is a pH, temperature and the concentration of the chemical itself depending process. The degradative plasmid pDOC encoding degradation of chlorpyrifos can be transferred to soil bacteria, and it is possible to use pDOC in bioaugmentation.