The effects of flagellar hook compliance on motility of monotrichous bacteria: A modeling study
The effects of flagellar hook compliance on motility of monotrichous bacteria: A modeling study
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DOI：
10.1063/1.4721416
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发表时间：
2012-06-01
影响因子：
4.6
通讯作者：
Gaffney, E. A.
中科院分区：
文献类型：
--
作者：
Shum, H.;Gaffney, E. A.
鞭毛细菌运动的一个关键结构是钩子，它将鞭毛细丝与细胞体中的马达连接起来。早期的游动细菌数学模型假定螺旋状的鞭毛绕其轴线刚性旋转，这与细胞体的轴线一致。有证据表明，钩子比鞭毛的其他部分更灵活，受此启发，我们开发了一种新的模型，允许自然直的钩子弯曲。钩子动力学基于Kirchhoff杆模型，该模型与边界元方法相结合，用于解决细菌与周围流体之间的粘性相互作用。对于在无界流体中游泳，我们发现使用刚性模型是很好的支持，因为在电机的几个旋转中，挂钩达到了平衡构型。然而，对于有效的游泳，钩子的刚度相对于由电机扭矩与钩子长度的乘积设置的比例存在约束。当钩子太灵活时，它的形状就不能保持，并且会产生很大的变形和应力。当钩子太硬时，鞭毛与细胞体的轴线不对齐，细胞“摇摆”，几乎没有净向前运动。我们还检查了游泳者对防滑表面的吸引力，发现稳定地靠近表面游泳的倾向可能对钩的刚性和细胞和鞭毛的精确形状的组合非常敏感。(C)2012年美国物理研究所。[http://dx.doi.org/10.1063/1.4721416]
A crucial structure in the motility of flagellated bacteria is the hook, which connects the flagellum filament to the motor in the cell body. Early mathematical models of swimming bacteria assume that the helically shaped flagellum rotates rigidly about its axis, which coincides with the axis of the cell body. Motivated by evidence that the hook is much more flexible than the rest of the flagellum, we develop a new model that allows a naturally straight hook to bend. Hook dynamics are based on the Kirchhoff rod model, which is combined with a boundary element method for solving viscous interactions between the bacterium and the surrounding fluid. For swimming in unbounded fluid, we find good support for using a rigid model since the hook reaches an equilibrium configuration within several revolutions of the motor. However, for effective swimming, there are constraints on the hook stiffness relative to the scale set by the product of the motor torque with the hook length. When the hook is too flexible, its shape cannot be maintained and large deformations and stresses build up. When the hook is too rigid, the flagellum does not align with the cell body axis and the cell "wobbles" with little net forward motion. We also examine the attraction of swimmers to no-slip surfaces and find that the tendency to swim steadily close to a surface can be very sensitive to the combination of the hook rigidity and the precise shape of the cell and flagellum. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4721416]