Biodegradation of the phenylurea herbicide isoproturon and its metabolites in agricultural soils.
Degradation of the phenylurea herbicide isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) and several phenylurea and aniline metabolites was studied in agricultural soils previously exposed to isoproturon. The potential for degradation of the demethylated metabolite 3-(4-isopropylphenyl)-1-methylurea in the soils was much higher compared to isoproturon. In the most active soil only 6% of added 14C-labelled isoproturon was mineralised to 14CO2 within 20 days while in the same period 45% of added 14C-labelled 3-(4-isopropylphenyl)-1-methylurea was mineralized. This indicates that the initial N-demethylation may be a limiting step in the complete mineralization of isoproturon. Repeated addition of 3-(4-isopropylphenyl)-1-methylurea to the soil and further subculturing in mineral medium led to a highly enriched mixed bacterial culture with the ability to mineralize 3-(4-isopropylphenyl)-1-methylurea. The culture did not degrade either isoproturon or the didemethylated metabolite 3-(4-isopropylphenyl)-urea when provided as sole source of carbon and energy. The metabolite 4-isopropyl-aniline was also degraded and utilised for growth, thus indicating that 3-(4-isopropylphenyl)-1-methylurea is degraded by an initial cleavage of the methylurea-group followed by mineralization of the phenyl-moiety. Several attempts were made to isolate pure bacterial cultures degrading 3-(4-isopropylphenyl)-1-methylurea or 4-isopropyl-aniline, but they were not successful.
Sørensen
S R
SR
Department of Geochemistry, Geological Survey of Denmark and Greenland, Copenhagen, Denmark.
Aamand
J
J
D001673:Biodegradation, Environmental; D002245:Carbon Dioxide / Q000378:metabolism; D006540:Herbicides / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008782:Methylurea Compounds / Q000737:chemistry / Q000378:metabolism*; D010671:Phenylurea Compounds; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*
D006540:Herbicides; D008782:Methylurea Compounds; D010671:Phenylurea Compounds; D012989:Soil Pollutants; D002245:Carbon Dioxide; C028904:isoproturon