Bacteria organize in a variety of collective states, from swarming—rapid surface exploration, to biofilms—highly dense immobile communities attributed to stress resistance. It has been suggested that biofilm and swarming are oppositely controlled, making this transition particularly interesting for understanding the ability of bacterial colonies to adapt to challenging environments. Here, the swarm to biofilm transition is studied in Bacillus subtilis by analyzing the bacterial dynamics both on the individual and collective scales. We show that both biological and physical processes facilitate the transition. A few individual cells that initiate the biofilm program cause nucleation of large, approximately scale-free, stationary aggregates of trapped swarm cells. Around aggregates, cells continue swarming almost unobstructed, while inside, trapped cells are added to the biofilm. While our experimental findings rule out previously suggested purely physical effects as a trigger for biofilm formation, they show how physical processes, such as clustering and jamming, accelerate biofilm formation.

中文翻译：

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群体向生物膜转变的生物物理方面

细菌以各种集体状态组织，从蜂拥而至——快速地表探索，到生物膜——归因于抗压性的高度密集的不动群落。有人提出，生物膜和蜂群受到相反的控制，这使得这种转变对于了解细菌菌落适应具有挑战性的环境的能力特别有趣。在这里，研究了群体到生物膜的转变枯草芽孢杆菌通过分析个体和集体尺度上的细菌动力学。我们表明，生物和物理过程都促进了这种转变。一些启动生物膜程序的单个细胞会导致大的、近似无标度的、静止的被困群细胞聚集体成核。在聚集体周围，细胞继续蜂拥而至，几乎不受阻碍，而在内部，被捕获的细胞被添加到生物膜中。虽然我们的实验结果排除了之前提出的纯物理效应作为生物膜形成的触发因素，但它们显示了物理过程（如聚集和干扰）如何加速生物膜的形成。