Abstract
<title>Abstract</title> <p>Plastic-associated biofilms formed in wastewater influent represent an early-stage plastisphere within wastewater treatment plants. However, it remains unclear whether they broadly enrich resistance-related risks or instead act as source-dependent interfaces that selectively reorganize wastewater-derived microbial and functional features. Here, we analyzed paired water-phase and polyethylene (PE)-biofilm samples established from raw influent wastewater collected from four wastewater treatment plants using 16S rRNA gene sequencing, shotgun metagenomics, and 16S-normalized qPCR targeting selected antibiotic resistance genes (ARGs) and mobile genetic element (MGE) markers. PE biofilms harbored bacterial assemblages that were distinct from, but strongly constrained by, their corresponding influent communities. Rather than passively retaining the broader wastewater microbiota, PE surfaces selectively favored specific attached taxa and tended to support lower alpha-diversity. The PE-associated resistome was not uniformly enriched but instead underwent compositional restructuring, with stronger signatures of multidrug resistance, disinfectant and biocide resistance, and efflux-related functions. Targeted quantitative PCR further supported this selective pattern: tet(39) and floR exhibited higher 16S-normalized abundances in PE biofilms, whereas the Integrall-derived marker Int02 showed no consistent PE-associated enrichment. Mobilome profiles were likewise marker-specific, and ARG–MGE co-variation was concentrated around selected wastewater-relevant ARGs, including sul1 and qacEΔ1, together with a group of plasmid-associated markers. Integrated module analysis further revealed that pathogen- and virulence-related, resistance, and mobility annotations formed distinct source-specific profiles rather than a single coordinated pattern of enrichment on PE. These findings indicate that PE biofilms in raw wastewater influent are not universal hotspots for ARG accumulation. Instead, they function as source-dependent, particle-associated interfaces that selectively restructure bacterial communities, resistomes, mobilomes, and pathogen- and virulence-related features. Risk assessment of wastewater plastisphere should therefore move beyond ARG abundance alone and account for the multidomain organization of microbial, resistance, mobility, and virulence-associated traits on particle surfaces.</p>