Divergent fates of antibiotic resistance genes in free-living versus particle-attached bacteria: An EPS stoichiometric framework

Antibiotic resistance genes (ARGs) in aquatic environments are conventionally surveyed as a bulk pool, yet partition across two ecologically distinct lifestyles—free-living (FL) and particle-attached (PA)—whose extracellular polymeric substance (EPS) chemistry, horizontal-gene-transfer (HGT) regimes, and treatment vulnerabilities differ fundamentally. We critically synthesize the FL/PA-resolved ARG literature and propose that the protein-to-polysaccharide (PN/PS) ratio of EPS is an integrative mechanistic axis linking environmental drivers, microbial physiology, and resistance gene fates. Although PA dominates total ARG abundance, the FL fraction is a high-risk reservoir whose health relevance is decoupled from abundance—more diverse, treatment-resistant, and transmission-relevant—yet rendered invisible by bulk-water monitoring through Simpson’s Paradox aggregation. We integrate these threads into the Lifestyle-Resistome Partitioning Model (LRPM), whose central hypothesis is that a single environmental trigger (N:P imbalance) propagates through the ppGpp stringent response to simultaneously drive EPS remodeling and integrase upregulation—a proposed cascade in which several links remain inferential; PN/PS serves as a proposed integrative readout governing aggregate architecture and HGT activity, consolidating ARGs in PA microniches while dispersing treatment-resistant ARGs in FL. The LRPM yields four operational implications: (i) size-fractionated monitoring is a statistical prerequisite; (ii) PN/PS measurement is the priority methodological advance; (iii) fraction-aware sequential treatment is mechanistically informed, with chlorination-before-sedimentation inadvisable based on current evidence; and (iv) catchment-scale N:P optimization emerges as an ARG co-benefit. Five testable predictions guide One-Health surveillance and management.