Sucrose Reshapes the Extracellular Protein–Peptide Landscape of Streptococcus mutans and Identifies Peptide Candidates With Antibiofilm Activity

The extracellular molecular landscape of oral bacteria remains underexplored beyond canonical secreted proteins. Here, we show that sucrose reshapes the culture-supernatant protein-peptide output of the cariogenic pathobiont Streptococcus mutans UA159. Integrating proteomics with stringent peptidomic source assignment revealed that sucrose remodeled the supernatant-detectable proteome toward surface/envelope- and cell-wall-associated features while reducing cytoplasmic, metabolic, and glucosyltransferase-associated signatures. In parallel, sucrose was associated with a distinct endogenous peptide layer. Among 34 stringently defined UA159-derived peptide candidates, 19 mapped to signal peptide regions, and many were preferentially detected under the sucrose condition. Functional screening of 16 successfully synthesized candidates identified two BHIS-associated signal-peptide-region peptides, SmuG15 and SmuV13, that reduced biofilm biomass and glucan-associated matrix signals when supplied exogenously, without detectable inhibition of planktonic growth in brain heart infusion (BHI). This separation between planktonic-growth and biofilm phenotypes is consistent with a biofilm-associated effect rather than detectable bacteriostatic activity under the planktonic-growth conditions tested. Together, these findings identify culture-supernatant peptides as sucrose-responsive extracellular outputs and highlight peptide candidates whose synthetic counterparts showed antibiofilm activity upon exogenous application. The study expands the molecular view of sucrose-driven cariogenic adaptation and provides a framework for discovering functional peptides from bacterial extracellular compartments.