We report the isolation of a Pseudomonas sp. which is able to transform imidacloprid and thiamethoxam under microaerophilic conditions in the presence of an alternate carbon source. This bacterium. Pseudomonas sp. 1G, was isolated from soil with a history of repeated exposure to imidacloprid. Both insecticides were transformed to nitrosoguanidine (=N-NO), desnitro (=NH), and urea (=O) metabolites and a transformation pathway is proposed. This is the first conclusive report of bacterial transformation of the 'magic nitro' group which is responsible for the insect selectivity of neonicotinoid insecticides. Crown Copyright (C) 2009 Published by Elsevier Inc. All rights reserved.