Dynamic motility selection drives population segregation in a bacterial swarm

Area of Science:

• Microbial Ecology
• Population Dynamics
• Biophysics

Background:

• Population expansion (range expansion) is common in natural and clinical settings.
• Space competition between subpopulations during expansion is influenced by growth and motility.
• Microbial communities, like bacterial swarms, serve as models for studying range expansion dynamics.

Purpose of the Study:

• To investigate the role of single-cell motility in space competition among heterogeneous bacterial populations during range expansion.
• To understand how motility differences influence the spatial structure and collective behaviors of expanding microbial populations.

Main Methods:

• Utilized bacterial swarms as a model system to observe range expansion.
• Analyzed single-cell motion characteristics, including speed and persistence time, in heterogeneous populations.
• Investigated the relationship between motility heterogeneity, spatial segregation, and collective drug tolerance.

Main Results:

• Motility heterogeneity promotes spatial segregation of bacterial subpopulations through a dynamic motility selection process.
• Speed-dependent persistence time bias in single-cell motion, likely due to cell-cell interactions, underlies this selection.
• Motility differences, rather than growth rate, significantly determine the short-term spatial structure of expanding populations.

Conclusions:

• Motility heterogeneity is a key factor in shaping the spatial organization of expanding microbial populations.
• Dynamic motility selection can lead to the spatial segregation of subpopulations with specific traits, such as transient drug tolerance.
• This segregation can contribute to the collective drug tolerance of swarming colonies by positioning tolerant cells at the colony edge.