Virus-host interactions driving the transfer of antibiotic resistance genes in a river-reservoir system under heavy rainfall

Global river systems are grappling with severe pollution from antibiotic resistance genes (ARGs), with river-reservoir (R-R) systems being a common feature in urban waterways. The intensified extreme rainfall events triggered by global climate change exacerbate the spread of ARGs posed by non-point source pollution and combined sewage overflows. This study employs a metagenomics approach to decipher the profile of ARGs and virus-host interactions driving their transfer under heavy rainfall in North Canal with extensive R-R systems. Results indicated that R-R systems contributed to ARGs reduction despite continuous discharge of treated wastewater in North Canal. The ARGs assembly is predominantly governed by stochastic process, and heavy rainfall enhances the dispersal capability. Nonetheless, the deterministic process determined the assembly of both microbial and viral community. Heavy rainfall not only significantly increased the abundance and diversity of ARGs within the rivers with minimal change in the reservoir, but also promotes the horizontal gene transfer of ARGs with higher conjugative mobility. Although the species accumulation curves approached saturation, no viruses carrying ARGs were detected among the 23,835 non-redundant vOTUs, and lytic phages-ARB interactions drove the ARGs reduction with higher VHRs, highlighting its contribution to the reduction ARGs in R-R system after heavy rainfall.