How the flagellum knows when to stop The bacterial flagellum is important in bacterial pathogenesis and biofilm formation. It is a rotary nanomotor that allows bacteria to propel themselves through liquids and across surfaces. Researchers interested in nanoscale robotics use the bacterial flagellum as a model for a machine that self-assembles on the nanoscale. Cohen et al. examined exactly how the flagellum precisely measures its shaft so that it spans, but does not extend beyond the edge of, the periplasm. The growing flagellum uses a mechanism by which it “senses” when it hits the outer membrane and stops growing. Changing the width of the periplasmic space by remodeling a particular lipid changed the length of the flagellar shaft. Science, this issue p. 197 The distal rod length of the bacterial flagellum is limited by the width of the periplasmic space. The bacterial flagellum exemplifies a system where even small deviations from the highly regulated flagellar assembly process can abolish motility and cause negative physiological outcomes. Consequently, bacteria have evolved elegant and robust regulatory mechanisms to ensure that flagellar morphogenesis follows a defined path, with each component self-assembling to predetermined dimensions. The flagellar rod acts as a driveshaft to transmit torque from the cytoplasmic rotor to the external filament. The rod self-assembles to a defined length of ~25 nanometers. Here, we provide evidence that rod length is limited by the width of the periplasmic space between the inner and outer membranes. The length of Braun's lipoprotein determines periplasmic width by tethering the outer membrane to the peptidoglycan layer.

中文翻译：

---

鞭毛驱动轴的纳米级长度控制需要撞击系留的外膜

鞭毛如何知道何时停止 细菌鞭毛在细菌发病机制和生物膜形成中很重要。它是一种旋转式纳米马达，可以让细菌在液体中和表面上推动自己。对纳米级机器人感兴趣的研究人员使用细菌鞭毛作为在纳米级自组装的机器的模型。科恩等人。确切地检查了鞭毛如何精确测量其轴以使其跨越但不超出周质的边缘。不断增长的鞭毛使用一种机制，当它碰到外膜并停止生长时，它会通过这种机制“感知”。通过重塑特定脂质来改变周质空间的宽度会改变鞭毛轴的长度。科学，这个问题 p。197 细菌鞭毛的远端杆长度受周质空间宽度的限制。细菌鞭毛体现了一个系统，在该系统中，即使与高度调节的鞭毛组装过程发生微小的偏差，也会消除运动性并导致负面的生理结果。因此，细菌已经进化出优雅而强大的调节机制，以确保鞭毛形态发生遵循既定的路径，每个组件自组装到预定的尺寸。鞭毛杆作为传动轴将扭矩从细胞质转子传递到外丝。棒自组装到约 25 纳米的定义长度。在这里，我们提供的证据表明，杆长度受到内膜和外膜之间周质空间宽度的限制。布劳恩的长度