Biodegradation of Neonicotinoid Insecticides Thiacloprid and Thiamethoxam by Microorganisms: Metabolic Process, Metabolic Enzymes and Toxicity Assessments of their Metabolites.

Abstract

The extensive agricultural use of neonicotinoid insecticides, particularly thiacloprid (THI) and thiamethoxam (THIA), has raised profound environmental and ecological concerns. Microbial bioremediation has emerged as a promising strategy to mitigate these impacts. While numerous microorganisms capable of degrading THI and THIA have been identified and characterized, the underlying degradation mechanisms remain poorly understood. This review provides a comprehensive examination of the microbial metabolic pathways involved in THI and THIA degradation, with a particular focus on the ecotoxicological effects of these compounds and their transformation products. Special emphasis is placed on the key catabolic enzymes in promoting the breakdown of these neonicotinoids, including nitrile hydratases (NHases), cytochrome P450 enzymes (CYPs), and aldehyde oxidases (AOXs). We place particular emphasis on the synergistic potential of microbial communities in enhancing degradation efficiency through complementary metabolic pathways, especially in environments contaminated with complex pesticide mixtures. Furthermore, we advocate for the integration of multi-omics technologies, computational biology, synthetic biology, and metabolic engineering to advance microbial biodegradation strategies. The insights presented in this review deepen our understanding of the enzymatic mechanisms underlying the microbial degradation of THI and THIA, highlighting their potential for mitigating neonicotinoid-induced environmental contamination.