Slow to Start, Free at Last: Dual Effects of Mucin on Escherichia coli Phage T4

Bacteriophages traversing the gastrointestinal tract are exposed to extreme physicochemical stresses that may rapidly compromise virion integrity and shape infection dynamics. While some phages bind to host-derived mucins at mucosal surfaces, the functional consequences of soluble mucin glycans for phage-host interactions remain incompletely understood. Here, we show that soluble mucin glycans exert dual effects on the Escherichia coli phage T4 by delaying infection initiation while simultaneously providing environmental virion stability. Mucin-coated T4 exhibits a lag in the onset of productive infection, consistent with transient steric occlusion from E. coli, yet without impairing overall phage progeny production once infection was established. We further show that E. coli can metabolize purified mucin, supporting a model in which dynamic remodeling of the mucin matrix gradually releases T4 and enables infection. Importantly, mucin coating substantially increases T4 survival under gastrointestinal-like stresses, including acidic pH and protease exposure. Moreover, we find that in a murine gut colonization model, a single oral dose of mucin-coated T4 displayed enhanced fecal persistence over a two-week period, which correlated with prolonged suppression of E. coli populations and delayed resolution of phage-associated functional shifts in the gut microbiome. Together, we find that that soluble mucin glycans actively shape T4 phage infection kinetics, virion stability, and ecological impact in the murine gut, and support mucin-based formulations as a strategy to extend the persistence and efficacy of orally delivered phages.