Degradation of mucin O-glycans by a human gut symbiont requires a complex enzyme repertoire and promotes colonization.

Bacteroides thetaiotaomicron expresses a >100-gene enzyme repertoire during growth on colonic mucin O-glycan substrates, enabling mucin degradation via 13 collective enzymes.

• Why it matters: The specific enzymatic pathways used by gut symbionts to break down colonic mucin O-glycans—and how this affects colonization—remain unclear, limiting targeted intervention strategies.
• What they did: The study profiled >100 expressed genes in Bacteroides thetaiotaomicron on different O-glycan substrates, then characterized 33 glycoside hydrolase enzymes to define a degradation pathway.
• The result: In vivo competition experiments linked multiple exo-acting enzymes targeting mucin capping structures to gut colonization, suggesting actionable targets to inhibit mucin degradation.

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