Nitrate-Induced Microbial Metabolic Activation and Community Composition Optimization Enhance the Anaerobic Biodegradation of Thiamethoxam

Abstract

This study investigated the impact of nitrate on the biodegradation potential of thiamethoxam (THM) in aquatic environments. It was found that the introduction of different nitrate concentrations significantly improved the anaerobic biodegradation efficiency of THM. Notably, the degradation rate of THM increased remarkably as nitrate concentration increased. As the nitrate concentration was elevated to 200 mg·L-1, the removal rate of THM significantly increased to 85.92%, which was 7.45 times higher than that of the control group. Analysis of results from Tafel, AC impedance (EIS), electron transport activity (ETSA), and nicotinamide adenine dinucleotide (NADH) revealed that the addition of nitrate enhanced the electrochemical activity of the system and the efficiency of electron transfer. Furthermore, nitrate promoted the secretion of extracellular polymers and activated the activity of related enzymes, such as nitrate reductase (NAR), nitrite reductase (NIR), and catalase (CAT). Macro-transcriptome analyses showed that nitrate addition changed the structure of the microbial community, regulated the expression of relevant functional genes, and increased microbial metabolic activity, thereby effectively accelerating the biodegradation of THM. This study provides new insights into the relationship between nitrate and the biological anaerobic degradation of THM.

Keywords: Nitrate, Enhanced, Thiamethoxam (THM), Anaerobic biodegradation, enzyme activity, Genetic analysis