The potential role of viruses in antibiotic resistance gene dissemination in activated sludge viromes

The dissemination of antibiotic resistance genes (ARGs) in activated sludge (AS) systems poses significant environmental and public health challenges. The role of viruses, primarily bacteriophages, in storing and spreading ARGs in AS systems remains largely unexplored. This study characterized the viral community, virus-associated ARGs (vir_ARGs), and mobile genetic elements (MGEs) of aerobic AS viromes from eight wastewater treatment plants (WWTPs) in eastern China. 78,604 viral operational taxonomic units (vOTUs) were identified, including 1685 temperate vOTUs (T-vOTUs). Five ARG types were detected in 37 vOTUs, indicating a low proportion of ARG-carrying viruses. The co-occurrence rate between vir_ARGs and MGEs was 37.83 %, and six ARG-carrying vOTUs contained multiple MGEs, indicating a transfer potential of vir_ARGs. Additionally, ARG and MGE profiles of AS metagenomes were analyzed to evaluate the transfer potential of phage activity on ARGs. The results showed that phage-associated MGEs showed a significant coupling with both the abundance and composition of ARGs, suggesting a potential role of phages in ARG propagation. These findings offer preliminary insights into understanding the viral resistome and its transfer potential in AS systems. Future research necessitates rigorous pure culture and molecular biology experiments to elucidate the precise mechanisms through which viruses contribute to the dissemination and persistence of ARGs.