Growth of bacterial biofilms at interfaces

In many ecological niches, growth of bacterial biofilms is mechanically coupled to their surroundings. However, how the mechanical environment shapes the growth of biofilms is still unknown. Using Vibrio cholerae as a model biofilm former, we investigate the growth of biofilms at the interface between a glass and a gel substrate. We find that the stiffness of the encasing gel determines the overall biofilm morphology. When surrounded by a soft gel, biofilms grow into a bulbous shape, that grows in a nearly shape-preserving manner, whereas when surrounded by a stiff gel, biofilms grow into a penny-like shape, that becomes apparently thinner over time. Furthermore, we elucidate the role that biofilm-surface adhesion plays on overall shape morphogenesis. Finally, we demonstrate the effect that shape has on the emergence of cell ordering and cell trajectories during biofilm development.