Ryan Shawn D, Ariel Gil, Be'er Avraham
Department of Mathematical Sciences, Kent State University, Kent, Ohio.
Department of Mathematics, Bar-Ilan University, Ramat Gan, Israel.
Biophys J. 2016 Jul 12;111(1):247-55. doi: 10.1016/j.bpj.2016.05.043.
Simultaneous acquisition of phase-contrast light microscopy and fluorescently labeled bacteria, moving within a dense swarm, reveals the intricate interactions between cells and the collective flow around them. By comparing wild-type and immotile cells embedded in a dense wild-type swarm, the effect of the active thrust generated by the flagella can be singled out. It is shown that while the distribution of angles among cell velocity, cell orientation, and the local flow around it is Gaussian-like for immotile bacteria, wild-type cells exhibit anomalous non-Gaussian deviations and are able to move in trajectories perpendicular to the collective flow. Thus, cells can maneuver or switch between local streams and jets. A minimal model describing bacteria as hydrodynamic force dipoles shows that steric effects, hydrodynamics interactions, and local alignments all have to be taken into account to explain the observed dynamics. These findings shed light on the physical mechanisms underlying bacterial swarming and the balance between individual and collective dynamics.
同时获取相差光学显微镜图像和在密集群体中移动的荧光标记细菌，揭示了细胞之间复杂的相互作用以及它们周围的集体流动。通过比较嵌入密集野生型群体中的野生型细胞和不能运动的细胞，可以单独分离出鞭毛产生的主动推力的影响。结果表明，对于不能运动的细菌，细胞速度、细胞方向及其周围局部流动之间的角度分布呈高斯分布，而野生型细胞则表现出异常的非高斯偏差，并且能够沿垂直于集体流动的轨迹移动。因此，细胞可以在局部流和射流之间进行机动或切换。一个将细菌描述为流体动力偶极子的最小模型表明，为了解释观察到的动力学，必须考虑空间效应、流体动力学相互作用和局部排列。这些发现揭示了细菌群体行为背后的物理机制以及个体动力学和集体动力学之间的平衡。
