Spatial modulation of individual behaviors enables collective decision-making during bacterial group migration

Coordination of individuals with diversity often requires sophisticated communications and high-order computational abilities. Microbial populations can exhibit diverse individualistic behaviors and yet can engage in collective migratory patterns with a spatially sorted arrangement of phenotypes following a self-generated attractant gradient. However, it’s unclear how individual bacteria without complex computational abilities can achieve the consistent group performance and determine their positions in the group while facing spatiotemporally dynamic stimuli. Here, we investigate the statistics of bacterial run-and-tumble trajectories during group migration. We discover that, despite of the constant migrating speed as a group, the individual drift velocity exhibits a spatially dependent structure that decreases from the back to the front of the group. The spatial modulation of individual stochastic behaviors constrains cells in the group, ensuring the coherent population movement with ordered patterns of phenotypes. These results reveal a simple computational principle for emergent collective behaviors from heterogeneous individuals.