The effect of nutrient-limited growth on floral pattern formation in yeast biofilms
Date:
Abstract: Yeast species have important impacts on human life, and in many applications it would be advantageous to control their growth. For example, yeasts are used extensively in food and drink production and in biotechnology, but are also a leading cause of persistent hospital-acquired infections. It is therefore of interest to understand the fundamental mechanisms that determine colony morphology. Yeast biofilms are complex systems in which growth is influenced by nutrient consumption, flow of extracellular fluid, and mechanical forces. In this work, we investigate the hypothesis that nutrient-limited growth is the mechanism by which patterns form. Analysis of experimental images shows that biofilms expand radially at a roughly constant speed, and undergo a transition from circular to floral morphology, which is characterised by the formation of finger-like ‘petals’. We use this data to parametrise a reaction-diffusion model with non-linear degenerate cell diffusion. In doing this, we show that two-dimensional travelling wave solutions to our model are linearly unstable to transverse perturbations for experimentally feasible parameters. There is good agreement between experimental floral patterns and predictions using the range of unstable wave numbers. Our model, which incorporates nutrient-limited growth alone, therefore provides a potential explanation for petal formation in yeast biofilms.