Mechano-self-regulation of bacterial size in growing colonies

We demonstrate that biomechanical forcing plays an important role as the driving force behind the dynamical self-regulation of cell size (or length) in growing bacterial colonies. In our experiments, the measured elongation rate decreases over time and depends on the areal packing density around each cell. To describe this phenomenon theoretically, we devise a cell-resolved model which includes as its key ingredient a force opposed to the growth process, accounting for mechano-self-regulation. Our model is analyzed analytically by a coarse-grained dynamical density functional theory and solved by cell-based computer simulations to predict how the strength of mechano-self-regulation depends on the bacterial size, the location in the colony and the local environment. The microscopic nature of this approach allows to quantify the effect of biomechanical interactions on the structure, composition and dynamical features of growing bacterial colonies.