Chemotactic migration of bacteria--their ability to direct multicellular motion along chemical gradients--is central to processes in agriculture, the environment, and medicine. However, studies are typically performed in bulk liquid, despite the fact that most bacteria inhabit heterogeneous porous media such as soils, sediments, and biological gels. Here, we directly visualize the migration of E. coli populations in 3D porous media. We find that pore-scale confinement is a strong regulator of chemotactic migration. Strikingly, cells use a different primary mechanism to direct their motion in confinement than in bulk liquid. Further, confinement markedly alters the dynamics and morphology of the migrating population--features that can be described by a continuum model, but only when standard motility parameters are substantially altered from their bulk liquid values. Our work thus provides a framework to predict and control the migration of bacteria, and active matter in general, in heterogeneous environments.

中文翻译：

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细菌在多孔介质中的趋化迁移

细菌的趋化迁移-它们沿着化学梯度引导多细胞运动的能力-对于农业，环境和医学过程至关重要。然而，尽管大多数细菌居住在异质多孔介质（例如土壤，沉积物和生物凝胶）中，但研究通常是在散装液体中进行的。在这里，我们直接可视化3D多孔介质中大肠杆菌种群的迁移。我们发现孔尺度限制是趋化迁移的强调节剂。引人注目的是，细胞在封闭状态下使用的主要机制不同于散装液体中的主要机制。此外，禁闭明显改变了人口迁移的动态和形态-这些特征可以用连续模型描述，但仅当标准运动参数与其液体总值有实质性变化时。因此，我们的工作为预测和控制异质环境中细菌和活性物质的迁移提供了一个框架。