Biochemical degradation pathway of dimethoate by Paracoccus sp. Lgjj-3 isolated from treatment wastewater

• DOI: 10.1016/j.ibiod.2009.10.007
• Publication Date: 2009-11-01T09:21:51Z
• Authors: Rong Li; Jingwei Zheng; Rong Wang; Yao Song; Qiming Chen; Xiujuan Yang; Shunpeng Li; Jiandong Jiang
• Keywords: Phosphoric acid

Abstract Dimethoate is a widely used organophosphorus insecticide often detected in the environment. A highly effective dimethoate-degrading Paracoccus sp. strain Lgjj-3 was isolated from treatment wastewater. Strain Lgjj-3 can utilize dimethoate as its sole carbon source for growth and degrade an initial concentration of 100 mg l −1 dimethoate to non-detectable levels within 6 h in liquid culture. During the degradation of dimethoate, seven metabolites, including dimethoate carboxylic acid, 2-(hydroxy(methoxy)phosphorylthio)acetic acid, O,O,S -trimethyl thiophosphorothioate, O -methyl O,S -dihydrogen phosphorothioate, phosphorothioic O,O,S -acid, O , O , S -trimethylphosphorothiate and O , O , O -trimethyl phosphoric ester, were successfully detected and identified based on MS/MS and GC–MS analysis. A biochemical degradation pathway of dimethoate by Paracoccus sp. Lgjj-3 is proposed for the first time. Dimethoate is first hydrolyzed by the scission of the amide bond to form dimethoate carboxylic acid, which is subsequently decarboxylated into O,O,S -trimethyl thiophosphorothioate. The produced O,O,S -trimethyl thiophosphorothioate is oxidized to form O , O , S -trimethylphosphorothiate and then further oxidized to form O,O,O -trimethyl phosphoric ester. O , O , S -trimethylphosphorothiate can also be hydrolyzed at the C–O bond to release a CH 3 group and cleavaged at the S–C bond through a hydrolytic pathway to form O -methyl O,S -dihydrogen phosphorothioate. Dimethoate carboxylic acid can also be oxidated at the P S bond to form the corresponding oxon derivative. Next, hydrolysis can occur at the C–O bond to form 2-(hydroxy(methoxy)phosphorylthio)acetic acid, which can be further hydrolyzed at the S–C bond to form O -methyl O,S -dihydrogen phosphorothioate. Phosphorothioic O,O,S -acid is finally formed by the hydrolysis of the C–O bond of O -methyl O,S -dihydrogen phosphorothioate to lose another CH 3 group.