Degradation of Selected Herbicides by Aquatic Microorganisms

摘要

Degradation of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) herbicide by pond water and pond sediment microorganisms was studied to assess the degradative pathway. An enrichment procedure was used to isolate microorganisms capable of degrading diuron and, while no such isolate could degrade diuron in pure culture, several mixed fungal/bacterial and mixed bacterial isolated cultures could either partially/totally degrade this herbicide. Studies using radiolabeled diuron (C-14 carbonyl group), mixed culture degradation, and analysis by thin-layer chromatography (TLC), showed that 24-28 day incubation with a mixed fungal/bacterial culture and mixed bacterial cultures gave 78-98% degradation (7 products) and 67-99% degradation (6 products), respectively. The mixed fungal/bacterial culture liberated carbon dioxide as 74-96% of the carbonyl label. TLC analysis indicated the major product formed by most cultures was 3,4-dichloroaniline. Detection of the demethylated derivatives, 3-(3,4-dichlorophenyl)-1-methyl urea and 3-(3,4-dichlorophenyl) urea, suggested a stepwise demethylation of diuron occurred. Similar studies with 2,6-dichlorobenzonitrile (dichlobenil) herbicide showed degradation products of 2,6-dichlorobenzoic acid and 2,6-dichlorobenzamide.