Protein-Dominated Adsorption and Protection on Viruses in Model EPS Components: Insight from Multiscale Mechanistic Analysis

Extracellular polymeric substances (EPS) as the core sewage sludge components play important roles in floc stability and pollutant adsorption. However, the molecular mechanisms underlying EPS-virus interactions and their environmental implications remain unclear. This study employed three representative model EPS components, i.e., proteins, polysaccharides, and humic substances, and systematically investigated EPS-virus interaction mechanisms with T7 bacteriophage as a virus surrogate. By integrating surface plasmon resonance analysis, double-layer agar plaque assays and qPCR, we demonstrated that proteins dominate virus adsorption and stability within simulated EPS matrices. With rapid protein-virus association (ka up to 106 M-1·s-1) and moderate binding affinities (KD in the 10-6-10-7 M range), roughly 60% of viral infectivity was preserved over 8 days, in contrast to the 4.58% observed in the control. By integrating Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, Fourier transform infrared spectroscopy, and molecular dynamics simulations, we further elucidated that adsorption is primarily governed by van der Waals forces, with electrostatic, hydrophobic, and hydrogen-bond interactions also involved. Moreover, the protein conformational rearrangements upon adsorption may further facilitate the formation of stable complexes. These findings provide mechanistic insights into the fate and potential EPS-mediated risks of viruses in engineered and natural aquatic environments, and also offer a theoretical basis for improving viral risk assessment.