Biomechanical feedback during confined biofilm growth revealed by single-cell resolution imaging

All living creatures interact with their external environment and bacterial cells are no exception. In nature, bacterial cells exist in the surface-attached community lifestyle embedded in an extracellular matrix, known as biofilms. In many conditions, biofilms grow inside a structured, confined environment. However, despite the importance of the bacteria-environment interaction, little is known as to how mechanical confinement interferes with the biofilm developmental program and how the proliferation of biofilm cells, in turn, deforms or even damages the surrounding environments as feedback to control the biofilm growth. In this presentation, we will integrate single-cell live imaging, finite element modeling, mechanics theories, and mutagenesis to investigate how Vibrio cholerae biofilms grow inside agarose gels. With single-cell resolution imaging, we found that overall biofilm morphology is susceptible to growth-induced mechanical stress and different degree of confinement. And biofilms behave as active soft matter with highly cell ordering. By using mutants lacking single or a combination of the vibrio polysaccharide (VPS) and accessory proteins, we investigated how cell ordering changes as a function of extracellular matrix components.