Streptococcus mutans Extracellular Vesicles Regulate Early Streptococcus sanguinis Nanoadhesion.

Area of Science:

• Oral microbiology
• Bacterial communication
• Biofilm dynamics

Background:

• Dental caries is a prevalent disease driven by oral biofilm dysbiosis.
• The interaction between Streptococcus mutans and Streptococcus sanguinis is crucial in early biofilm formation.
• Bacterial extracellular vesicles (bEVs) mediate microbial communication, but their role in interspecies adhesion is unclear.

Purpose of the Study:

• To investigate how Streptococcus mutans-derived bEVs influence Streptococcus sanguinis nanoadhesion and initial biofilm formation.
• To assess the impact of bEVs from planktonic cultures versus biofilms grown on native or glycated collagen.

Main Methods:

• Isolation and characterization of bacterial EVs (bEVs) using nanoparticle tracking analysis and transmission electron microscopy.
• Quantification of bacterial adhesion forces and unbinding events using atomic force microscopy-based single-cell force spectroscopy.
• Assessment of early biofilm architecture using optical coherence tomography.

Main Results:

• Planktonic-derived bEVs enhanced S. sanguinis adhesion, while bEVs from collagen-bound S. mutans biofilms reduced adhesion forces.
• bEVs from glycated collagen matrices showed a more pronounced suppression of S. sanguinis adhesion.
• Nanoscale adhesion changes translated to altered biofilm architecture: planktonic bEVs promoted denser biofilms, while biofilm-derived bEVs led to sparser colonization.

Conclusions:

• S. mutans bEVs exhibit context-dependent modulation of S. sanguinis, enhancing adhesion in planktonic conditions and suppressing it in biofilms.
• This biphasic behavior may be a strategy for niche domination during caries initiation.
• Collagen glycation significantly influences bEV function, highlighting the role of the host matrix in microbial interactions.