Toxicological Analysis of Acetamiprid Degradation by the Dominant Strain Md2 and Its Effect on the Soil Microbial Community

Microbial degradation is acknowledged as a viable and eco-friendly approach for diminishing residues of neonicotinoid insecticides. This study reports the dominant strain of Md2 that degrades acetamiprid was screened from soil and identified as <i>Aspergillus heterochromaticus</i>, and the optimal degradation conditions were determined. Research indicated that the degradation of Md2 to 100 mg/L acetamiprid was 55.30%. Toxicological analyses of acetamiprid and its metabolites subsequently revealed that acetamiprid and its metabolites inhibited the germination of cabbage seed, inhibited the growth of <i>Escherichia coli</i>, and induced the production of micronuclei in the root tip cells of faba beans. Based on the analysis of metabolic pathways, it has been determined that the primary metabolic routes of acetamiprid include N-demethylation to form IM-2-1 and oxidative cleavage of the cyanoimino group to produce IM-1-3. Using 16S rRNA high-throughput sequencing, the results showed that acetamiprid and Md2 elevated the relative abundance of <i>Acidithiobacillus</i>, <i>Ascomycetes</i>, and <i>Stramenobacteria</i>, with increases of 10~12%, 6%, and 9%, respectively, while reducing the relative abundance of <i>Acidobacteria</i>, <i>Chlorobacteria</i>, <i>Ascomycetes</i>, and <i>Sporobacteria</i>, with decreases of 15%, 8%, 32%, and 6%, respectively. The findings will facilitate the safety evaluation of the toxicological properties of neonicotinoid insecticides, their biodegradable metabolites, and associated research on their degradation capabilities.