title: Biodegradation of imidacloprid by an isolated soil microorganism.
abstract: Imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine), a chloronicotinyl insecticide used to control biting and sucking insects, is very persistent in the soil with a half-life often greater than 100 days. Although a few soil metabolites have been reported in the literature, there are no reports of imidacloprid-degrading soil microorganisms. Our objectives were to discover, isolate, and characterize microorganisms capable of degrading imidacloprid in soil. Two soil-free stable enrichment cultures in N-limited media were obtained that degraded 19 mg L(- 1) (43%) and 11 mg L(- 1) (16%) of the applied imidacloprid, and produced about 19 mg L(- 1) 6-chloronicotinic acid in three weeks. Enrichment media without microorganisms had no loss of imidacloprid. Strain PC-21, obtained from the enrichment cultures, degraded 37% to 58% of 25 mg L(- 1) imidacloprid in tryptic soy broth containing 1 g L(- 1) succinate and D-glucose at 27 degrees C incubation over a period of three weeks. Trace amounts of NO(3)(-)/NO(2)(-)were produced and six metabolites were characterized by high performance liquid chromatography (HPLC) using (14)C-methylene-imidacloprid and liquid chromatograph-electrospray-mass spectrometer (LC-MS). Two of the metabolites were identified as imidacloprid-guanidine and imidacloprid-urea by HPLC standards and LC-MS. During the experiment, 6-chloronicotinic acid was not produced. Less than 1% of the applied (14)C was incorporated into the microbial biomass and no (14)CO(2) was detected. Strain PC-21, identified as a species of Leifsonia by PCR amplification of a 500 bp sequence of 16s rRNA, cometabolized imidacloprid.
authors.affiliation: Department of Microbiology, Iowa State University, Iowa, USA.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Anhalt
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Moorman
authors.forename: William C
authors.initials: WC
authors.lastname: Koskinen
mesh_terms: D000192:Actinomycetales / Q000302:isolation & purification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D002853:Chromatography, Liquid / Q000379:methods; D007093:Imidazoles / Q000493:pharmacokinetics*; D007306:Insecticides / Q000493:pharmacokinetics*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000493:pharmacokinetics*; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011865:Radioisotope Dilution Technique; D012987:Soil / Q000032:analysis; D012988:Soil Microbiology
chemical_list: D002250:Carbon Radioisotopes; D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D012336:RNA, Ribosomal, 16S; D012987:Soil; C082359:imidacloprid