Host-derived O-glycans inhibit toxigenic conversion by a virulence-encoding phage in Vibrio cholerae

Pandemic and endemic strains of Vibrio cholerae arise from toxigenic conversion by the CTX phi bacteriophage, a process by which CTX phi infects nontoxigenic strains of V. cholerae. CTX phi encodes the cholera toxin, an enterotoxin responsible for the watery diarrhea associated with cholera infections. Despite the critical role of CTX phi during infections, signals that affect CTX phi-driven toxigenic conversion or expression of the CTX phi-encoded cholera toxin remain poorly characterized, particularly in the context of the gut mucosa. Here, we identify mucin polymers as potent regulators of CTX phi-driven pathogenicity in V. cholerae. Our results indicate that mucin-associated O-glycans block toxigenic conversion by CTX phi and suppress the expression of CTX phi-related virulence factors, including the toxin co-regulated pilus and cholera toxin, by interfering with the TcpP/ToxR/ToxT virulence pathway. By synthesizing individual mucin glycan structures de novo, we identify the Core 2 motif as the critical structure governing this virulence attenuation. Overall, our results highlight a novel mechanism by which mucins and their associated O-glycan structures affect CTX phi-mediated evolution and pathogenicity of V. cholerae, underscoring the potential regulatory power housed within mucus.