BIODEGRADATION OF ORGANOPHOSPHORUS INSECTICIDES BY BACTERIA ISOLATED FROM TURF GREEN SOIL

Several organophosphate-degrading bacteria were isolated from test tur f green soil using clear zones formed around their colonies on plates supplemented with organophosphate isoxathion. The degrading activity o f the isolates for isoxathion was tested by incubation in liquid cultu res and evaluated by gas chromatography. Strain B-5 exhibited the high est isoxathion degrading ability in the isolates and it was identified as an Arthrobacter sp. A high concentration of nutrients in the media affected the isoxathion degrading activity of strain B-5. The bacteri um could not utilize isoxathion as a sole source of carbon and phospho rus. The degradation products of isoxathion by B-5 washed cells were i dentified as its hydrolysis products, 3-hydroxy-5-phenylisoxazole and diethylthiophosphoric acid, suggesting that strain hydrolyzes the hete rocycle ester bond in isoxathion. Arthrobacter sp. strain B-5 also hyd rolyzed diazinon, parathion, EPN, fenitrothion, isofenphos, chlorpyrif os, and ethoprophos at rates dependent on the substrate. Of the organo phosphorus insecticides examined, isofenphos was affected most by the hydrolytic activity of the bacterium, which completely removed the com pound (10 mg/l) from cultures within l-h incubation.