Disinfection by-products induce population-level antibiotic resistance via mutation-driven competition and membrane...

Disinfection by-products (DBPs), persistent non-antibiotic stressors in aquatic environments, impose underrecognized evolutionary pressure on microbial communities. Here, evolution experiments with Escherichia coli MG1655 exposed to environmentally relevant concentrations of five representative DBPs for 30 days revealed a 4- to 16-fold increase in resistance to DNA-targeting antibiotics, including norfloxacin, ciprofloxacin, and trimethoprim. The fluorescent plasmid-based co-culture system visualizes the evolutionary transition from individual mutations to population-wide resistance. DBP-induced mutants exhibit enhanced metabolic activity, increased biofilm formation, and upregulated efflux systems, collectively conferring a competitive advantage under sustained chemical stress. Crucially, this adaptive process is mediated by defined genetic alterations (e.g., in fimH and lacl), and is orchestrated through systematic membrane reprogramming under the control of a global stress response regulatory network. Transcriptomic revealed activation of two-component systems, ABC transporters, and lipopolysaccharide biosynthesis pathways, providing a molecular foundation for population-level resistance. These results demonstrate that long-term exposure to DBPs promote the emergence and stabilization of population-level antibiotic resistance via membrane reprogramming, underscoring the need to consider the evolutionary impacts of non-antibiotic contaminants in microbial risk assessment and water treatment strategies.