In Vivo Microrheology Reveals Local Elastic and Plastic Responses Inside 3D Bacterial Biofilms

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Bacterial biofilms are complex 3D living materials with diverse functions.
• Measuring in vivo mechanical properties of biofilms at the cellular scale has been a significant challenge.

Purpose of the Study:

• To develop and validate a noninvasive method for measuring the internal mechanical properties of living biofilms with cellular resolution.
• To investigate the anisotropic elastic and plastic responses of biofilms under shear stress.

Main Methods:

• Tracking thousands of individual cells within living Vibrio cholerae biofilms under varying shear stress conditions.
• Applying a general mechanical model inferred from cellular tracking data.
• Utilizing microrheology and force-inference techniques.

Main Results:

• Revealed anisotropic elastic and plastic responses in cell displacement and reorientation within biofilms.
• Obtained spatially-resolved measurements of the biofilm's elastic modulus.
• Correlated mechanical properties with the spatial distribution of polysaccharides in the biofilm matrix.

Conclusions:

• The introduced noninvasive microrheology and force-inference approach provides a general framework for studying mechanical properties in living materials.
• This method enables high spatial resolution measurements within biofilms, advancing the study of their biomechanics.