In vivo Microrheology Reveals Local Elastic and Plastic Responses Inside Three-dimensional Bacterial Biofilms.

Abstract

Bacterial biofilms are highly abundant three-dimensional (3D) living materials capable of performing complex biomechanical and biochemical functions, including programmable growth, self-repair, filtration, and bioproduction. Methods to measure internal mechanical properties of biofilms in vivo with spatial resolution on the cellular scale have been lacking. Here, we tracked thousands of cells inside living 3D biofilms of the bacterium Vibrio cholerae during and after the application of shear stress, for a wide range of stress amplitudes, periods, and biofilm sizes, which revealed anisotropic elastic and plastic responses of both cell displacements and cell reorientations. Using cellular tracking to infer parameters of a general mechanical model, we obtained spatially-resolved measurements of the elastic modulus inside the biofilm, which correlate with the spatial distribution of the polysaccharides within the biofilm matrix. The non-invasive microrheology and force-inference approach introduced here provides a general framework for studying mechanical properties with high spatial resolution in living materials. This article is protected by copyright. All rights reserved.