Dynamic motility selection drives population segregation in a bacterial swarm

Ecological models usually take growth rate fitness as the essential driver of population dynamics. However, as a widespread natural phenomenon, population expansion in space (or range expansion) is often governed by both motility and growth. Microbial communities offer unique systems to study how individual’s motility contributes to space competition among heterogeneous microbial populations during range expansion. Here we show that motility heterogeneity can promote the spatial segregation of sub-populations in structured microbial communities via a dynamic motility selection mechanism. Our findings are relevant to microbial stress response and microbial ecology. The results may also provide new insight to range expansion in other biological systems, such as tumor invasion and collective stress tolerance of cancer cells in densely packed environments.