Abstract:To systematically elucidate the effects of long-term, low-dose exposure to benzalkonium chloride (BAC) on gut microbiota composition and metabolic homeostasis, Drosophila melanogaster W1118 was employed as the model organism. Acute and chronic toxicity assays were conducted, combined with 16S rRNA sequencing and non-targeted metabolomics analyses. The results showed that the lethal effects of BAC exhibited clear dose- and time-dependent characteristics; under acute exposure, the 48 h median lethal concentration (LC50) was determined to be 0.54%. In chronic exposure, the survival rate of the 1/10 LC50 treatment group was reduced to 70% from day 9 onward.16S rRNA sequencing revealed that gut microbial structure was significantly perturbed by BAC exposure, with Firmicutes decreasing from 16.33% to 5.93%, Bacteroidota increasing from 0.04% to 0.61%, and Proteobacteria increasing from 83.57% to 91.19%. Metabolomics analysis identified 386 significantly altered metabolites (137 upregulated and 249 downregulated), mainly involved in purine metabolism, amino-acid biosynthesis and metabolism, and glycerophospholipid metabolism. Correlation analysis further indicated that differential bacterial taxa such as Proteobacteria and Bacteroidota were closely associated with key metabolites including AMP, ADP, and glutamate.In summary, long-term low-dose BAC exposure was found to markedly disrupt the gut microbial community and metabolic network of fruit flies, thereby disturbing core physiological processes such as energy conversion, cell proliferation, and membrane-lipid metabolism. This study provides an important reference for the food safety risk analysis and toxicity assessment of quaternary ammonium compounds.
