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(16-23) Biodegradation of organophosphorus by its degrading micro-organisms isolated from mangrove sediment. Wong, Jo*,1, Wong, Y.S.1, Tam, Nora1, 1 Department of Biology and Chemistry, City University of Hong Kong, Hong Kong SAR, China, Hong Kong ABSTRACT- Other than organochlorine pesticides, organophosphorus(OP) pesticides made a major contribution to improvements in agricultural output and in the control of disease vectors. The EPA Office of Pesticides Programs (OPP) Health Effects Division (HED) reports that diazinon and chlorpyrifos, the commonly used pesticides, is the leading cause of acute reaction to pesticide use. It is also associated with numerous environmental hazards, including surface water contamination. Therefore, diazinon and chlorpyrifos were chosen for studying. The possibility of isolating OP-degrading bacteria from natural contaminated mangrove sediments was explored. Surface soil(SS) and rhizosphere soil(RS) samples collected from Mai Po(mangrove site located in the western Hong Kong) were enriched in mineral salt medium(MSM) supplement with 1ppm OP pesticides. The ability of these mix cultures in degrading OP in liquid cultures were also examined. An increase in bacterial biomass was found by measuring the optical density. Liquid-liquid phase extraction was employed and the amount of diazinon and chlorpyrifos degraded was analyzed by GC-FPD. Both pesticides were degraded by the mix culture of microorganisms. More than 20% and 15% of OPs were degraded by the mix culture from SS and mix culture from RS at late log phase respectively. Mix cultures were subjected to lower concentrations of OP pesticides and checked with their degradation ability. Different bacteria were isolated from the enriched cultures and their ability to degrade was examined. One of the isolate was chosen and undergo further investigation. The degradation by that isolate under 100ppb and 500ppb OP pesticides was determined. Both OP pesticides were having more than 15% degradation. Key words: biodegradation , mangrove soil, organophosphorus pesticides, bacteria |
