Size-distribution dynamics in growing bacterial colonies with mechano-sensing

Inspired by our recent work on smectic liquid crystals in extreme confinement [1-2], we develop a microscopic theory for growing bacteria colonies based on classical dynamical density functional theory (DDFT). Our first-principles approach pays special attention to the particle length as a key ingredient and explicitly accounts for growth and cell division [3]. The length-dependent interactions between the particles, which naturally arise in the framework of DDFT, ensure that the bacteria colony does not grow indefinitely due to spatial constraints. Our model thus accounts for an environmental feedback on the effective growth rate of individual agents, which we interpret as a form of mechano-sensing.

As a first step to evaluate our theory, we focus on the degrees of freedom related to the particle length [3]. Doing so, we analytically predict the form of the stationary length distribution which depends on the interplay of growth rate, mechano-sensing and fluctuations. We then demonstrate that the final composition of the colony undergoes a transition from diverse (many different lengths) to compressed (predominantly short bacteria) upon increasing the strength of mechanical interactions. The predictions of our probabilistic model are corroborated by particle-resolved stochastic simulations of the growth process. Our insights will help to quantify the effect of mechanical interactions on structure, composition and dynamical aspects of experimental bacterial colonies.