Laboratoire Matière et Systèmes Complexes, UMR CNRS 7057, University Paris Diderot, 75205 Paris Cedex 13, France.
Laboratoire Matière et Systèmes Complexes, UMR CNRS 7057, University Paris Diderot, 75205 Paris Cedex 13, France
Proc Natl Acad Sci U S A. 2017 Jun 6;114(23):5958-5963. doi: 10.1073/pnas.1703997114. Epub 2017 May 23.
How systems are endowed with migration capacity is a fascinating question with implications ranging from the design of novel active systems to the control of microbial populations. Bacteria, which can be found in a variety of environments, have developed among the richest set of locomotion mechanisms both at the microscopic and collective levels. Here, we uncover, experimentally, a mode of collective bacterial motility in humid environment through the depinning of bacterial droplets. Although capillary forces are notoriously enormous at the bacterial scale, even capable of pinning water droplets of millimetric size on inclined surfaces, we show that bacteria are able to harness a variety of mechanisms to unpin contact lines, hence inducing a collective slipping of the colony across the surface. Contrary to flagella-dependent migration modes like swarming, we show that this much faster "colony surfing" still occurs in mutant strains of lacking flagella. The active unpinning seen in our experiments relies on a variety of microscopic mechanisms, which could each play an important role in the migration of microorganisms in humid environment.
系统如何获得迁移能力是一个引人入胜的问题，其影响范围从设计新型主动系统到控制微生物种群。细菌可以在各种环境中找到，它们在微观和集体层面上发展出了最丰富的运动机制。在这里，我们通过细菌液滴去钉实现了在潮湿环境中集体细菌运动的一种模式，通过实验揭示了这一模式。尽管在细菌尺度上，毛细作用力是非常巨大的，甚至能够将毫米大小的水滴固定在倾斜的表面上，但我们表明细菌能够利用各种机制来解开水滴的接触线，从而诱导菌落集体在表面上滑动。与依赖鞭毛的迁移模式（如群体游动）不同，我们表明，这种快得多的“菌落冲浪”即使在缺乏鞭毛的突变菌株中也会发生。我们实验中观察到的主动去钉依赖于各种微观机制，这些机制在微生物在潮湿环境中的迁移中可能都起着重要作用。
