Emergent Properties in Streptococcus mutans Biofilms Are Controlled through Adhesion Force Sensing by Initial...

Area of Science:

• Microbiology
• Biofilm Science
• Bacterial Adhesion

Background:

• Bacterial adhesion to surfaces alters gene expression, leading to unique biofilm properties.
• Understanding the role of environmental adhesion forces in these emergent properties is crucial for biofilm research.

Purpose of the Study:

• To investigate how environmental adhesion forces influence gene expression in *Streptococcus mutans*.
• To determine the role of quorum sensing in mediating adhesion-force-induced gene expression.
• To introduce and define the concept of "adhesion force sensitivity of genes."

Main Methods:

• Atomic force microscopy was used to measure adhesion forces of *S. mutans* on various substrata.
• Gene expression analysis was performed on wild-type and quorum-sensing-deficient *S. mutans* biofilms.
• Gene expression was correlated with adhesion forces at different biofilm heights and ages.

Main Results:

• Initial bacterial adhesion forces were low, but stationary forces varied with substratum hydrophobicity.
• Gene expression, particularly *brpA*, was sensitive to adhesion forces in wild-type biofilms.
• Adhesion-force-controlled gene expression was absent in the quorum-sensing-deficient mutant and limited to the lower biofilm layers.

Conclusions:

• Environmental adhesion forces act as external triggers for emergent biofilm properties via quorum sensing.
• The concept of "adhesion force sensitivity of genes" explains bacterial adaptation to surfaces.
• Information about substratum surfaces is transmitted up to 20-30 μm within the biofilm, highlighting communication limits.