Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, 78712, USA.
Department of Mathematics, Bar-Ilan University, Ramat Gan, 52000, Israel.
Sci Rep. 2018 Oct 25;8(1):15823. doi: 10.1038/s41598-018-34192-2.
Swarming bacteria are an example of a complex, active biological system, where high cell density and super-diffusive cell mobility confer survival advantages to the group as a whole. Previous studies on the dynamics of the swarm have been limited to easily observable regions at the advancing edge of the swarm where cells are restricted to a plane. In this study, using defocused epifluorescence video imaging, we have tracked the motion of fluorescently labeled individuals within the interior of a densely packed three-dimensional (3D) region of a swarm. Our analysis reveals a novel 3D architecture, where bacteria are constrained by inter-particle interactions, sandwiched between two distinct boundary conditions. We find that secreted biosurfactants keep bacteria away from the swarm-air upper boundary, and added antibiotics at the lower swarm-surface boundary lead to their migration away from this boundary. Formation of the antibiotic-avoidance zone is dependent on a functional chemotaxis signaling system, in the absence of which the swarm loses its high tolerance to the antibiotics.
群体游动细菌是一个复杂、活跃的生物系统的例子，其中高细胞密度和超扩散的细胞迁移赋予了整个群体生存优势。之前对群体动态的研究仅限于群体前进边缘的易于观察区域，在这些区域中，细胞被限制在一个平面上。在这项研究中，我们使用离焦荧光视频成像，跟踪了在群体内部高密度的三维（3D）区域内荧光标记个体的运动。我们的分析揭示了一种新的 3D 结构，其中细菌受到颗粒间相互作用的限制，夹在两个不同的边界条件之间。我们发现，分泌的生物表面活性剂使细菌远离群体空气的上边界，而在群体下表面边界添加抗生素会导致它们远离这个边界迁移。抗生素回避区的形成依赖于功能化的趋化信号系统，在没有该系统的情况下，群体对抗生素的高耐受性会丧失。
