Isoproturon degradation as affected by the growth of two algal species at different concentrations and pH values.
Metabolism of [14C-u-phenyl]isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] by two soil and freshwater microorganisms, green alga Chlorella kesslerei and cyanobacterium Anabaena inaequalis, was studied as a function of pH, pesticide concentration, and incubation time. Metabolized isoproturon, in the media, ranged from 0% (Chlorella at pH 5.5 after 1 d) to 22% (Anabaena at pH 5.5 after 10 d). Twenty-five percent faster degradation of isoproturon by Anabaena occurred at pH 5.5 versus pH 7.5, when measured over 10 d. Increased 14C incorporation into tissue, with time and at lower pH, was due mainly to bioaccumulation of [14C]isoproturon and/or its metabolites in the cells. Metabolic degradation resulted in four identifiable (by TLC) metabolites. Based on this, a degradation pathway is proposed, involving mono- and di-N-demethylation, hydroxylation of the isopropyl moiety, and hydrolysis to 4-isopropylaniline. Similarity in the metabolites produced suggests that the enzyme systems responsible for metabolizing isoproturon are almost identical in both photosynthetic micro-algae.
Mostafa
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US Department of Agriculture, Agricultural Research Service, Plant Sciences Inst, Beltsville, MD 20705, USA. mostafaf@ba.ars.usda.gov
Helling
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D017033:Anabaena / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002247:Carbon Isotopes; D002708:Chlorella / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D006540:Herbicides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008782:Methylurea Compounds / Q000378:metabolism*; D010671:Phenylurea Compounds; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000378:metabolism
D002247:Carbon Isotopes; D006540:Herbicides; D008782:Methylurea Compounds; D010671:Phenylurea Compounds; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; C028904:isoproturon