Evaluating Streptococcus mutans Strain Dependent Characteristics in a Polymicrobial Biofilm Community

Area of Science:

• Microbiology
• Oral Health
• Biotechnology

Background:

• Streptococcus mutans is a key cariogenic bacterium involved in dental caries.
• Understanding S. mutans behavior in polymicrobial communities is essential for caries prevention.
• Strain-dependent variations in S. mutans biofilm formation can impact virulence.

Purpose of the Study:

• To investigate strain-dependent differences in cariogenic biofilm formation by Streptococcus mutans.
• To compare S. mutans behavior in mono-species versus polymicrobial in vitro biofilm models.
• To analyze the impact of different environmental conditions on S. mutans within complex biofilms.

Main Methods:

• Developed mono-species and multispecies in vitro caries biofilm models using clinical isolates of S. mutans and other oral bacteria.
• Evaluated biofilm composition (total and live bacteria) using live/dead PCR.
• Assessed biofilm architecture via scanning electron microscopy (SEM) and analyzed virulence gene expression using quantitative PCR.

Main Results:

• In mono-species biofilms, S. mutans strains showed similar responses to carbohydrate sources, with sucrose yielding the most biomass.
• In polymicrobial biofilms, S. mutans from caries-free patients favored Lactobacillus casei, while S. mutans from caries patients dominated the biofilm.
• Upregulation of virulence genes (srtA, gtfB, ftf, spaP, gbpB, luxS) was observed in S. mutans-dominant biofilms.

Conclusions:

• Individual S. mutans strains exhibit distinct biofilm characteristics in polymicrobial settings, not evident in simple mono-species models.
• Environmental conditions significantly alter the composition and function of S. mutans within polymicrobial biofilms.
• The developed biofilm model offers a novel approach to assess environmental influences on the oral biofilm microbiome.