  Growth in confined spaces can drive cellular populations through a jamming
transition from a fluid-like state to a solid-like state. Experiments have
found that jammed budding yeast populations can build up extreme compressive
pressures (over 1MPa), which in turn feed back onto cellular physiology by
slowing or even stalling cell growth. Using extensive numerical simulations, we
investigate how this feedback impacts the mechanical properties of model jammed
cellular populations. We find that feedback directs growth toward
poorly-coordinated regions, resulting in an excess number of cell-cell contacts
that rigidify cell packings. Cell packings posses anomalously large shear and
bulk moduli that depend sensitively on the strength of feedback. These results
demonstrate that mechanical feedback on the single-cell level is a simple
mechanism by which living systems can tune their population-level mechanical
properties.
