To Biofilm or Not To Biofilm: A biophysical threshold for biofilm formation

Bacteria are ubiquitous in our daily lives, either as motile planktonic cells or as surface-attached biofilms. These different states have considerable functional implications for processes in agriculture, environment, industry, and medicine; hence, it is critically important to understand the conditions that regulate the onset of biofilm formation. Unfortunately, the transition from the planktonic to biofilm state depends on a dizzyingly complex array of cellular and environmental factors. To address this issue, here, we develop a generally-applicable biophysical model that captures essential features of the interplay between motility-mediated dispersal and biofilm formation. Using this model, we establish a universal rule predicting how the onset and extent of biofilm formation depend collectively on cell concentration and motility, nutrient diffusion and consumption, chemotactic sensing, and autoinducer secretion. Our work thus provides a key first step toward quantitatively predicting and controlling biofilm formation in diverse and complex settings.