Mucin promotes pneumococcal colonization via autolysis suppression and tryptophan-mediated immune modulation

Mucin promotes Streptococcus pneumoniae nasopharyngeal colonization by suppressing LytA autolysis and inducing tryptophan biosynthesis, enabling survival against macrophage killing.

• Why it matters: Mucus is usually treated as a host barrier, but how it shapes pneumococcal persistence as an asymptomatic colonizer is unclear.
• What they did: The work shows mucin inhibits LytA enzymatic activity, prolonging survival and limiting pneumolysin release, and it triggers de novo tryptophan production and extracellular release.
• The result: Tryptophan biosynthesis is critical for survival under macrophage killing, and disrupting it abolishes both colonization and invasive disease, with transcriptomics linking tryptophan to a bactericidal macrophage state.

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