Cross-Kingdom Cell-to-Cell Interactions in Cariogenic Biofilm Initiation

Area of Science:

• Microbiology and Oral Health
• Biophysics of Microbial Interactions

Background:

• Candida albicans forms polymicrobial biofilms with Streptococcus species.
• Streptococcus gordonii binds directly to C. albicans hyphae.
• Streptococcus mutans interacts with C. albicans via extracellular glucans.

Purpose of the Study:

• To investigate the biophysical properties of Candida-Streptococcus interactions at the single-cell level.
• To determine the influence of fungal surface glucans on binding forces and early biofilm formation.

Main Methods:

• Single-cell atomic force microscopy was used to measure binding forces.
• Interactions were examined between Candida albicans, Streptococcus mutans, and Streptococcus gordonii.
• Experiments were conducted with and without in situ glucans on the fungal surface.

Main Results:

• Streptococcus gordonii exhibited higher binding force to C. albicans than Streptococcus mutans (~2-fold).
• Streptococcus mutans binding force increased dramatically (~6-fold) on glucan-coated C. albicans.
• Enhanced S. mutans binding led to larger early biofilms and S. mutans dominance in a 3-species model.

Conclusions:

• Extracellular glucans on Candida albicans selectively favor Streptococcus mutans binding.
• This biophysical interaction mechanism promotes Streptococcus mutans dominance in cariogenic biofilms.
• Understanding these cross-kingdom interactions is crucial for developing targeted biofilm control strategies.