Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri; Department of Genetics, Washington University in St. Louis, St. Louis, Missouri.
Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri.
Biophys J. 2019 Apr 2;116(7):1292-1304. doi: 10.1016/j.bpj.2019.02.012. Epub 2019 Feb 26.
The effects of cilium length on the dynamics of cilia motion were investigated by high-speed video microscopy of uniciliated mutants of the swimming alga, Chlamydomonas reinhardtii. Cells with short cilia were obtained by deciliating cells via pH shock and allowing cilia to reassemble for limited times. The frequency of cilia beating was estimated from the motion of the cell body and of the cilium. Key features of the ciliary waveform were quantified from polynomial curves fitted to the cilium in each image frame. Most notably, periodic beating did not emerge until the cilium reached a critical length between 2 and 4 μm. Surprisingly, in cells that exhibited periodic beating, the frequency of beating was similar for all lengths with only a slight decrease in frequency as length increased from 4 μm to the normal length of 10-12 μm. The waveform average curvature (rad/μm) was also conserved as the cilium grew. The mechanical metrics of ciliary propulsion (force, torque, and power) all increased in proportion to length. The mechanical efficiency of beating appeared to be maximal at the normal wild-type length of 10-12 μm. These quantitative features of ciliary behavior illuminate the biophysics of cilia motion and, in future studies, may help distinguish competing hypotheses of the underlying mechanism of oscillation.
通过对游泳藻类衣藻的单纤毛突变体的高速视频显微镜观察，研究了纤毛长度对纤毛运动动力学的影响。通过 pH 冲击去纤毛，并允许纤毛在有限的时间内重新组装，获得短纤毛细胞。纤毛的拍打频率是从细胞体和纤毛的运动估计的。从每个图像帧中的纤毛拟合的多项式曲线中量化了纤毛波形的主要特征。最值得注意的是，周期性拍打直到纤毛达到 2 到 4 μm 之间的临界长度才出现。令人惊讶的是，在表现出周期性拍打的细胞中，所有长度的拍打频率都相似，只有随着长度从 4 μm 增加到正常的 10-12 μm，频率略有下降。随着纤毛的生长，波形平均曲率（弧度/μm）也保持不变。纤毛推进的力学指标（力、扭矩和功率）都与长度成比例增加。拍打时的机械效率似乎在正常的野生型 10-12 μm 长度时达到最大值。这些纤毛行为的定量特征阐明了纤毛运动的生物物理学，并且在未来的研究中，可能有助于区分潜在振荡机制的竞争假说。
