Petroff Alexander P, Wu Xiao-Lun, Libchaber Albert
Laboratory of Experimental Condensed Matter Physics, The Rockefeller University, New York, New York 10065, USA.
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Phys Rev Lett. 2015 Apr 17;114(15):158102. doi: 10.1103/PhysRevLett.114.158102.
We investigate a new form of collective dynamics displayed by Thiovulum majus, one of the fastest-swimming bacteria known. Cells spontaneously organize on a surface into a visually striking two-dimensional hexagonal lattice of rotating cells. As each constituent cell rotates its flagella, it creates a tornadolike flow that pulls neighboring cells towards and around it. As cells rotate against their neighbors, they exert forces on one another, causing the crystal to rotate and cells to reorganize. We show how these dynamics arise from hydrodynamic and steric interactions between cells. We derive the equations of motion for a crystal, show that this model explains several aspects of the observed dynamics, and discuss the stability of these active crystals.
我们研究了一种由已知游动速度最快的细菌之一——大硫螺旋菌所展现的新型集体动力学形式。细胞会在表面自发地组织成一个由旋转细胞构成的、视觉上引人注目的二维六边形晶格。当每个组成细胞旋转其鞭毛时，会产生一种类似龙卷风的流动，将相邻细胞拉向自身并围绕自身旋转。当细胞相对于其相邻细胞旋转时，它们会相互施加力，导致晶体旋转且细胞重新组织。我们展示了这些动力学是如何由细胞间的流体动力学和空间相互作用产生的。我们推导了晶体的运动方程，表明该模型解释了所观察到的动力学的几个方面，并讨论了这些活性晶体的稳定性。
