Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People's Republic of China.
Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, People's Republic of China.
Proc Natl Acad Sci U S A. 2020 Mar 3;117(9):4693-4700. doi: 10.1073/pnas.1917789117. Epub 2020 Feb 14.
Population expansion in space, or range expansion, is widespread in nature and in clinical settings. Space competition among heterogeneous subpopulations during range expansion is essential to population ecology, and it may involve the interplay of multiple factors, primarily growth and motility of individuals. Structured microbial communities provide model systems to study space competition during range expansion. Here we use bacterial swarms to investigate how single-cell motility contributes to space competition among heterogeneous bacterial populations during range expansion. Our results revealed that motility heterogeneity can promote the spatial segregation of subpopulations via a dynamic motility selection process. The dynamic motility selection is enabled by speed-dependent persistence time bias of single-cell motion, which presumably arises from physical interaction between cells in a densely packed swarm. We further showed that the dynamic motility selection may contribute to collective drug tolerance of swarming colonies by segregating subpopulations with transient drug tolerance to the colony edge. Our results illustrate that motility heterogeneity, or "motility fitness," can play a greater role than growth rate fitness in determining the short-term spatial structure of expanding populations.
种群扩张，亦称分布区扩张，在自然界和临床环境中都很普遍。在分布区扩张过程中，异质亚种群之间的空间竞争对种群生态学至关重要，它可能涉及多种因素的相互作用，主要是个体的生长和运动性。结构化微生物群落为研究分布区扩张过程中的空间竞争提供了模型系统。在这里，我们使用细菌群体来研究单细胞运动性如何在分布区扩张过程中促进异质细菌种群之间的空间竞争。我们的结果表明，运动性异质性可以通过动态运动性选择过程促进亚种群的空间隔离。单细胞运动的速度相关的持久时间偏差赋予了这种动态运动性选择，这可能是由于密集群体中细胞之间的物理相互作用所致。我们进一步表明，动态运动性选择可以通过将具有短暂药物耐受性的亚种群隔离到菌落边缘，从而有助于群体的集体药物耐受性。我们的结果表明，运动性异质性（或“运动适应性”）比增长率适应性更能决定扩张种群的短期空间结构。
