Data corresponding to our paper on "Chemotactic smoothing of collective migration"

Collective migration -- the directed, coordinated motion of many
self-propelled agents -- is a fascinating emergent behavior exhibited by
active matter that has key functional implications for biological systems.
Extensive studies have elucidated the different ways in which this
phenomenon may arise. Nevertheless, how collective migration can persist
when a population is confronted with perturbations, which inevitably arise
in complex settings, is poorly understood. Here, by combining experiments
and simulations, we describe a mechanism by which collectively migrating
populations smooth out large-scale perturbations in their overall
morphology, enabling their constituents to continue to migrate together.
We focus on the canonical example of chemotactic migration of Escherichia
coli, in which fronts of cells move via directed motion, or chemotaxis, in
response to a self-generated nutrient gradient. We identify two distinct
modes in which chemotaxis influences the morphology of the population:
cells in different locations along a front migrate at different velocities
due to spatial variations in (i) the local nutrient gradient and in (ii)
the ability of cells to sense and respond to the local nutrient gradient.
While the first mode is destabilizing, the second mode is stabilizing and
dominates, ultimately driving smoothing of the overall population and
enabling continued collective migration. This process is autonomous,
arising without any external intervention; instead, it is a
population-scale consequence of the manner in which individual cells
transduce external signals. Our findings thus provide insights to predict,
and potentially control, the collective migration and morphology of cell
populations and diverse other forms of active matter.