Rapid Thiamethoxam Biodegradation by <i>Paenarthrobacter nicotinovorans</i> GY-1: Mechanistic Insights and Nitro-Reductive Pathway Elucidation

The neonicotinoid insecticide thiamethoxam (THX) poses ecological risks and requires efficient bioremediation strategies. We isolated a highly efficient THX-degrading strain, Paenarthrobacter nicotinovorans GY-1, from contaminated agricultural soil. Under response surface-optimized conditions, GY-1 achieved an unprecedented THX degradation rate of 2.08 mg·L –1 ·h –1, the highest reported for a microorganism to our knowledge. Transcriptomics, enzyme assays, and carbon-source profiling showed that strain GY-1 suppresses glycolysis and reprograms central metabolism when THX is used as the sole nitrogen source. Q-TOF MS and 1D/2D NMR analyses unequivocally determined the structures of two purified intermediates, THX-1 and THX-2, providing direct structural evidence for nitro-reduction and deimination during THX biodegradation. On the basis of these confirmed intermediates, we proposed a nitro-reductive bacterial transformation pathway. This work reveals a microbial adaptation mechanism and provides a potent biocatalyst for the eco-friendly remediation of THX-contaminated environments.