Ricard Alert

Nonuniform growth and surface friction determine bacterial biofilm morphology on soft substrates

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Shape transformations during an organism's development often arise from mechanical instabilities driven by nonuniform growth. A remarkable example is the formation of 3D wrinkles in bacterial biofilms growing on soft substrates, which may enhance the availability of nutrients and signaling molecules. To investigate the formation of biofilm wrinkle patterns, we developed a chemomechanical model that incorporates nutrient-limited inhomogeneous growth, surface friction, and the ensuing mechanical stresses and deformations. We predict the spatiotemporal stress field in a growing biofilm and how it dictates the formation of 3D biofilm morphology. Our model provides insight into the observed stages of expansion of Vibrio cholerae biofilms and suggests that universal mechanical principles may underlie the formation of 3D morphologies in biofilms across species.