A Markovian Approach towards Bacterial Cell Size Control and Homeostasis

Regardless recent developments, the mechanisms coupling growth and division to achieve cell size homeostasis are still not well understood. Herein we propose a Markovian growth/division theoretical model for rod-shaped bacteria, that we complement with experimental and computational approaches, to reconcile current knowledge. In this context we show that size control relies on the limited efficiency of the division machinery and that classifying cell sizes as a function of their prospective septa provides a compelling framework to understand growth and division. Our results reveal that size homeostasis in wild-type E. coli cells depends mainly on three cell populations and that the incremental rule is a general consequence, and not the cause, of a memoryless process that is compatible with a well-defined length scale set by cells to orchestrate division. Altogether, our study sheds light on the processes that lead to homeostasis in rod-shaped bacteria and paves the way to understand the problem of size regulation in other organisms.