Seasonality Determines the Variations of Biofilm Microbiome and Antibiotic Resistome in a Pilot-Scale Chlorinated Drinking Water Distribution System Deciphered by Metagenome Assembly

The microbial community and antibioticresistome were exploredduring prolonged biofilm formation in a pilot-scale chlorinated DWDSusing metagenome assembly. Understanding the biofilm microbiome and antibiotic resistomeevolutionin drinking water distribution systems (DWDSs) is crucial to ensurethe safety of drinking water. We explored the 10 month evolution ofthe microbial community, antibiotic resistance genes (ARGs), mobilegene elements (MGEs) co-existing with ARGs and pathogenic ARG hosts,and the ARG driving factors in DWDS biofilms using metagenomics assembly.Sampling season was critical in determining the microbial communityand antibiotic resistome shift. Pseudomonas was the primary biofilm colonizer, and biofilms diversified moreas the formation time increased. Most genera tended to cooperate toadapt to an oligotrophic environment with disinfectant stress. Biofilmmicrobial community and antibiotic resistome assembly were mainlydetermined by stochastic processes and changed with season. Metagenomeassembly provided the occurrence and fates of MGEs co-existing withARGs and ARG hosts in DWDS biofilms. The abundance of ARG- and MGE-carryingpathogen Stenotrophomonas maltophilia was high in summer. It primarily harbored the aph(3)-IIb, multidrug transporter, smeD,and metallo-beta-lactamase ARGs, which were transferredvia recombination. The microbial community was the most crucial factordriving the antibiotic resistance shift. We provide novel insightsabout the evolution of pathogens and ARGs and their correlations inDWDS biofilms to ensure the safety of drinking water.