Abstract

The increasing presence of disinfection by-products (DBPs) and antibiotic resistance genes (ARGs) in drinking water systems has raised significant concerns. However, the effects of elevated chlorine and haloacetic acids (HAAs) on ARGs conjugative transfer remain unclear. This study investigates the impacts of elevated chlorine concentrations on RP4 plasmid-mediated ARGs conjugative transfer in a system containing HAAs at relevant drinking water concentrations. Specifically, the research explores the mechanisms at both genomic and phenotypic mechanisms. It focuses on external processes as well as internal cellular responses. The effects of trichloroacetic acid (TCAA) and iodoacetic acid (IAA), along with chlorination, on bacterial survival and conjugative transfer were evaluated. Treatments with TCAA, IAA, and chlorine altered several key cellular functions, including membrane permeability, oxidative stress (ROS generation), and energy metabolism (ATP production). Additionally, key genes involved in these processes were quantified through RT-qPCR. The findings provide novel mechanistic insights into how TCAA and IAA are associated with enhanced ARGs conjugative transfer and the inhibitory roles of chlorine residuals in this process. This study underscores the need to understand the interplay between DBPs and ARGs in drinking water systems. It further suggests that proper management of chlorine residuals could help mitigate the spread of antibiotic resistance.