The shapes of most bacteria are imparted by the structures of their peptidoglycan cell walls, which are determined by many dynamic processes that can be described on various length scales ranging from short-range glycan insertions to cellular-scale elasticity^1-11. Understanding the mechanisms that maintain stable, rod-like morphologies in certain bacteria has proved to be challenging due to an incomplete understanding of the feedback between growth and the elastic and geometric properties of the cell wall^3,4,12-14. Here, we probe the effects of mechanical strain on cell shape by modelling the mechanical strains caused by bending and differential growth of the cell wall. We show that the spatial coupling of growth to regions of high mechanical strain can explain the plastic response of cells to bending⁴ and quantitatively predict the rate at which bent cells straighten. By growing filamentous Escherichia coli cells in doughnut-shaped microchambers, we find that the cells recovered their straight, native rod-shaped morphologies when released from captivity at a rate consistent with the theoretical prediction. We then measure the localization of MreB, an actin homologue crucial to cell wall synthesis, inside confinement and during the straightening process, and find that it cannot explain the plastic response to bending or the observed straightening rate. Our results implicate mechanical strain sensing, implemented by components of the elongasome yet to be fully characterized, as an important component of robust shape regulation in E. coli.

中文翻译：

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机械应变传感与大肠杆菌细胞形状恢复有关。

大多数细菌的形状是由它们的肽聚糖细胞壁的结构决定的，这些结构是由许多动态过程决定的，这些过程可以在从短程聚糖插入到细胞级弹性^1-11的各种长度尺度上进行描述。事实证明，由于对生长与细胞壁的弹性和几何特性之间的反馈不完全了解，因此了解在某些细菌中保持稳定的杆状形态的机制具有挑战性^3,4,12-14. 在这里，我们通过模拟由细胞壁的弯曲和差异生长引起的机械应变来探索机械应变对细胞形状的影响。我们表明，生长与高机械应变区域的空间耦合可以解释细胞对弯曲的塑性响应⁴并定量预测弯曲细胞伸直的速率。通过在环形微室中培养丝状大肠杆菌细胞，我们发现这些细胞在以与理论预测一致的速率从圈养中释放时恢复了它们笔直的、原生的棒状形态。然后，我们测量了 MreB 的定位，这是一种对细胞壁合成至关重要的肌动蛋白同系物，在限制内和拉直过程中，发现它不能解释塑料对弯曲的反应或观察到的拉直率。我们的结果暗示机械应变传感，由尚未完全表征的细长体组件实现，作为大肠杆菌中稳健形状调节的重要组成部分。