Isolation, Identification And Characterization Of Triazophos Degrading Bacteria

Triazophos (TAP) is a kind of mid-toxic organophosphorus pesticides with a broad spectrum killing many pests. Recently, it has more and more widespread applications as an alternative for high toxicity and residues pesticides in agricultural production, such as methyl parathion. It can never be ignored that the long-term utilization of TAP would produce serious environmental problems due to its toxicity. Therefore, it is significant to resolve the problem of how to effectively degrade the triazophos residues, prevent and repair environmental pollution. In the meantime, both food safety and health of rural residents also should be paid more attention. At present, mainly physical and biochemical approaches are used to degrade the triazophos, for example physical cleaning, chemical hydrolysis and chemical oxidation. Although these methods are effective, its high cost and incompleted degradation will be not suitable for long-term widely using. On the contrast, bio-removal of Triazophos is thorough and environmental friendly during the mild conditions. Developing the technology of triazophos degradation is mainly to find a sort of biological resources like micro-organisms. However, the recent studies concerning organophosphorus pesticide-degrading bacteria has not too much enough, it is very urgent to developed more triazophos bio-degradable strains.This study reported that ten bacterial strains selected from the activated sludge of a sludge pool in QiChun pesticide factory with the ability to degrade TAP. Four strains were choosen to further elucidate the ability of TAP-degrading. Through morphological identification that four strains showed a straight rod, Gram-negative, facultative anaerobic, peritrichate, movement. Four strains have the general characteristics of Enterobacter based on the biochemical-physiological identified. Combined with 16SrDNA molecular identification demonstrated that three of them belonging to Enterobacter sp., named the Enterobacter sp.HS-C5, Enterobacter sp.HS-C6, Enterobacter sp.HS-C10; another one belonging to Sheigella sp., named the Sheigella sp.HS-C8.Growth characteristics of strains showed that four degrading bacteria optimum growth temperature are 30℃and 35℃; the main optimum growth pH value is between 7.0 and 8.0. The optimal carbon sources of strains HS-C5, HS-C6, HS-C10 is glucose and the optimal carbon source of strain HS-C8 is maltose. The most suitable nitrogen sources of strains HS-C5, HS-C6, HS-C10 is yeast and the most suitable nitrogen source of strain HS-C8 is ammonium chloride. At the TAP concentration of 50 mg/L, pH 8.0, temperature 30℃, the four strains can degrade triazophos best. The maximum tolerant concentration of four triazophos degradation strains reached at 500 mg/L. A preliminary study of degradation characteristics using UV scanning spectrum suggested that the four bacteria have certain degradation ability of triazophos.