Isolation, Identification And Characterization Of Organophosphorus-degrading Strains

Pesticides play an important role in the control of plant diseases and insect pests. But they also destroy the environment seriously and leave great toxicity to human heath. Biodegradation, especial the degradation by microorganism, can ease this kind disadvantage. In this research, several strains with potential ability of degradation for organophosphorus pesticides were isolated from the activated sludge polluted by organophosphorus pesticides. It is identified that strains, YL3 and YL8, were members of the genera Arthrobacter. sp. by means of microcopy, biochemistry and genetic techniques.It is found that these strains can grow well in the medium with methylparathion or p-nitrophenol as the sole source of carbon. Strain YL8 can decrease 50mg/L methylparathion by about 90% in 5h and no p-nitrophenol could be observed with a UV spectrophotometer. It can also completely degrade 50mg/L p-nitrophenol in 7h. However, the lag period was much longer when the concentration of p-nitrophenol was increased. It needs about 13h to start the degradation when the p-nitrophenol concentration was 100mg L-1 and about 22h were needed to degrade it completely.The strain YL3 has the same character with strain YL8. When grown with methylparathion as the sole source of carbon, it was found that the optimal degradation for methylparathion was taken place during the first 7h with approximate 80% of methylparathion. It needed about 11h when YL3 strain was incubated using 50mg L-1 p-nitrophenol as sole carbon source and no p-nitrophenol was tested with a UV spectrophotometry. About 11h was needed to begin the rapid degradation of p-nitrophenol when the p-nitrophenol concentration was 100mg L-1 and 19h was needed to degrade it completely.None of degradation plasmid had been determined by several methods. It was presumed that these strains had embodied no this kind plasmid and the degrading-gene may orient in bacterial chromosome DNA.