Heterogeneous mechanical property inside 3D bacterial biofilms

Bacterial biofilm communities are estimated to be the most abundant biomaterial on Earth. While biofilms cause disadvantages in our lives such as clogging industrial pipes, forming dental plaque and contributing to human infections, biofilms also have been studied as programmable multifunctional biological materials in bioengineering and material science. The cell-to-cell interactions within biofilms are mediated by a viscoelastic extracellular matrix, which gives them high resistance to chemical agents like antibiotics and makes them mechanically difficult to remove. Therefore, understanding biofilm formation and its mechanical properties is a critical challenge in various research fields.

We performed measurements of elasticity and plasticity by combining microfluidic control for biofilm growth and deformation, three-dimensional live-cell imaging, and machine learning-based image analysis [1]. As a result, we successfully measured the coordinate displacement and orientation change of individual cells under biofilm deformation. Additionally, by assuming a spring model for the cell-to-cell interactions and fitting the measured values with the model, we clarified that the spring constant gradually decreases from the inside to the outside. That spatial distribution of spring constant correlates to the spatial distribution of polysaccharides within the biofilm matrix [2].