Potential pathogens drive ARGs enrichment during biofilms formation on environmental surfaces

The enrichment of antibiotic resistance genes (ARGs) on environmental surfaces is a fundamental question in microbial ecology. Understanding the processes driving ARG variations can provide clues into their transfer mechanisms between phases and offer insights for public health management. In this study, we examined microbiota, potential pathogen, and ARG dynamics on two common environment surfaces-polyvinyl chloride (PVC) and carbon steel (CS)-under environmental stress (induced by landfill leachate flow) in a Center for Disease Control and Prevention Biofilm Reactor using metagenomics and quantitative polymerase chain reaction-Chip techniques. Contrary to the expected changes in biofilms morphology and physiochemical properties, microbiota, potential pathogens, and ARGs exhibited a divergence-convergence pattern, primarily shaped by attachment surface properties and, subsequently, biofilm maturity during biofilms formation. During this process, ARG levels in biofilms gradually increased to and exceeded the levels in the surrounding environment, but with a distinct structure (P < .05). Furthermore, 1.93- and 3.05-fold increases in the concentrations of mobile genetic elements intI-1 in PVC and CS biofilms, respectively, suggested their important role in the transfer and spread of ARGs within the biofilm matrix. Although potential pathogens were less abundant (3.48%-5.63%) in the biofilms microbiota, they accounted for 18.28%-45.16% of the ARG hosts and harbored multiple ARGs. Pathogens significantly impacted ARG enrichment (Procrustes analysis: P = .0136, M2 = 0.34) although microbiota development also influenced this process (P = .0385, M2 = 0.67). These results suggest that pathogens are key in shaping ARG enrichment in biofilms. Our findings provide dynamic insights into resistome enrichment on environmental surfaces.