Concentric patterns of cell size in proliferating bacterial colonies with self-inhibiting growth

Cells modulate their growth in response to a variety of environmental cues. Mechanical responses in particular occur in many microorganisms, such as bacteria and yeast, and can affect colony morphologies and growth dynamics. In this talk, we consider a proliferating bacterial colony whose constituents' growth is inhibited by growth-induced mechanical stress. Discrete particle simulations of a growing colony show the emergence of concentric-ring patterns in cell size whose structure is closely tied to the individual stress response. Motivated by these observations, we derive a continuum theory that accounts for microscopic size statistics and macroscopic colony mechanics. Analytical solutions of this theory demonstrate excellent agreement with the particle simulations, and show the concentric patterns arise from anisotropically accumulated resistance to growth over many cell cycles. These solutions also show stress sensing can reduce overall stress within the colony and prevent exponential growth, resulting in asymptotically linear growth of the colony radius over time.