Macromolecular Science and Engineering Center, University of Michigan, Ann Arbor, Michigan, USA.
Biophys J. 2010 Jan 6;98(1):12-7. doi: 10.1016/j.bpj.2009.09.044.
To study the swimming of a peritrichous bacterium such as Escherichia coli, which is able to change its swimming direction actively, we simulate the "run-and-tumble" motion by using a bead-spring model to account for: 1), the hydrodynamic and the mechanical interactions among the cell body and multiple flagella; 2), the reversal of the rotation of a flagellum in a tumble; and 3), the associated polymorphic transformations of the flagellum. Because a flexible hook connects the cell body and each flagellum, the flagella can take independent orientations with respect to the cell body. This simulation reproduces the experimentally observed behaviors of E. coli, namely, a three-dimensional random-walk trajectory in run-and-tumble motion and steady clockwise swimming near a wall. We show that the polymorphic transformation of a flagellum in a tumble facilitates the reorientation of the cell, and that the time-averaged flow-field near a cell in a run has double-layered helical streamlines, with a time-dependent flow magnitude large enough to affect the transport of surrounding chemoattractants.
为了研究能够主动改变游动方向的周毛菌（如大肠杆菌）的游动方式，我们使用珠子-弹簧模型模拟“跑-跌”运动，以考虑：1）细胞体和多个鞭毛之间的水动力和机械相互作用；2）在跌打中鞭毛旋转方向的反转；以及 3）鞭毛的相关多态转换。由于柔性钩连接细胞体和每个鞭毛，鞭毛可以相对于细胞体独立定向。该模拟再现了大肠杆菌的实验观察到的行为，即在跑跌运动中呈现三维随机漫步轨迹，以及在靠近壁面时稳定地顺时针游动。我们表明，跌打中鞭毛的多态转换有助于细胞的重新定向，并且在跑中细胞附近的时均流场具有双层螺旋流线，其随时间变化的流场大小足以影响周围化学引诱剂的输运。
