Metagenomic approach reveals the fates and mechanisms of antibiotic resistance genes exposed to allicins during waste activated sludge fermentation: Insight of the microbial community, cellular status and gene regulation.

This work revealed the impacts of exogeneous allicins on the antibiotic resistance genes (ARGs) variations during waste activated sludge (WAS) fermentation process. The overall abundance of ARGs was respectively reduced by 4.84 and 9.42% in presence of 0.01 and 0.05 g allicin/g TSS. Allicins disrupted the EPS structure and increased the permeability of cell membranes, which resulted in the release of ARGs for subsequent removal. Allicins also reduced intracellular ATP levels, which was disadvantageous to ARGs dissemination. Besides, allicins affected the microbial community and decreased the abundance of potential hosts based on bacterial taxa-ARGs network analysis. Moreover, the metabolic pathways and genetic expressions (i.e., two-component system, quorum sensing, and SOS response) involved in ARGs propagation were down-regulated, which caused the ARGs alleviation in allicins-stressed reactors. Overall, the simultaneous responses of cellular status, bacterial host, and genetic regulation accounted for the effective ARGs reduction induced by allicins during WAS fermentation.