Metabolism of the Neonicotinoid Insecticides Acetamiprid and Thiacloprid by the Yeast Rhodotorula mucilaginosa Strain IM-2

A yeast identified as Rhodotorula mucilaginosa strain IM-2 was able to degrade acetamiprid (AAP) and thiacloprid (THI) in sucrose mineral salt medium with half-lives of 3.7 and 14.8 days, respectively, while it did not degrade imidacloprid and imidaclothiz. Identification of metabolites indicated that R. mucilaginosa IM-2 selectively converted AAP and THI by hydrolysis of AAP to form an intermediate metabolite IM 1-3 and hydrolysis of THI to form an amide derivative, respectively. Metabolite IM 1-3 had no insecticidal activity, while the THI amide showed considerable insecticidal activity but was 15.6 and 38.6 times lower than the parent THI following oral ingestion and a contact test against the horsebean aphid Aphis craccivora, respectively. The inoculated R. mucilaginosa IM-2 displayed biodegradability of AAP and THI in clay soils.