Biotin Limitation Attenuates Streptococcus mutans Cariogenicity by Disrupting Metabolic Flux and Virulence Pathways

Our previous metagenomic analysis revealed higher frequencies of biotin-related genes (i.e., bioY, bioM, bccP) in caries-active children, indicating a potential role of biotin in caries pathogenesis. This study investigated a biotin limitation strategy against the primary cariogenic bacterium Streptococcus mutans (S. mutans), including its effects on cariogenic phenotypes, gene expression, and metabolomics.

S. mutans UA159 was cultured in biotin-free medium supplemented with different biotin concentrations. The cariogenic phenotypes of the strain, including growth kinetics, biofilm formation, exopolysaccharide production, lactate synthesis, acid/oxidative tolerance, and membrane fluidity, were measured and compared across biotin concentrations. Biofilm architecture was visualized via confocal laser-scanning microscopy and scanning electron microscopy. Quantitative real-time polymerase chain reaction was employed to analyze the expression of genes associated with virulence and biotin metabolism. Metabolomic analysis was performed to characterize metabolic perturbations induced by biotin limitation in S. mutans.

Under biotin limitation, S. mutans exhibited significantly reduced cariogenic phenotypes, accompanied by cell elongation and reduced membrane fluidity. At the molecular level, biotin limitation suppressed the expression of key virulence-associated genes and induced a compensatory upregulation of genes involved in biotin uptake and biotin-dependent carboxylases. Metabolomic analysis under biotin-limited conditions in S. mutans revealed perturbed pathways in central carbon metabolism and nucleotide metabolism.

Biotin limitation significantly reduced the cariogenic potential of S. mutans by disrupting metabolic flux and virulence gene expression, highlighting biotin uptake and metabolism as potential targets for anticaries therapies.