Characterization and Metabolic Analysis of Domesticated Anaerobic Bacteria for Effective Thiamethoxam Bioremediation: Enzymatic, Genetic, and Pathway Insights

Abstract

The extensive use of neonicotinoid insecticides (NEOs), particularly thiamethoxam (THM), poses significant risks to both the ecological environment and human health, emerging as a critical environmental issue that requires immediate attention. In this study, anaerobic bacteria were successfully domesticated under THM stress. The results showed that the anaerobic bacteria could effectively degrade THM, with a degradation efficiency of 20-30% within 7 days. Bacterial community analysis identified Escherichia-Shigella, Acinetobacter, Delftia, Enterobacter, and Pseudomonas as the dominant genera at the genus level. During the THM degradation process, a decline in bacterial urease activity was observed, accompanied by a rise in catalase (CAT) activity, while β-galactosidase activity remained stable. Functional gene analysis of the macro-transcriptome revealed significant upregulation of genes related to the citrate cycle (TCA), oxidative phosphorylation, protein translocation, nitrogen metabolism, and the bacterial secretion system. DFT calculations and LC-MS/MS analyses identified three potential degradation pathways for THM, with nine characterized intermediates. In conclusion, the degradation performance and mechanism of THM by anaerobic bacteria were investigated for the first time. This study provides a theoretical basis for the biological treatment and ecological remediation of neonicotinoid pesticide wastewater.

Keywords: Thiamethoxam, anaerobic biodegradation, degradation pathways, DFT calculations