Institute of Biomechanics and Medical Engineering, AML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
Research Center of Applied Physics, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
Soft Matter. 2021 Mar 4;17(8):2042-2049. doi: 10.1039/d0sm02075c.
Turgor pressure and envelope elasticity of bacterial cells are two mechanical parameters that play a dominant role in cellular deformation, division, and motility. However, a clear understanding of these two properties is lacking because of their strongly interconnected mechanisms. This study established a nanoindentation method to precisely measure the turgor pressure and envelope elasticity of live bacteria. The indentation force-depth curves of Klebsiella pneumoniae bacteria were recorded with atomic force microscopy. Through combination of dimensional analysis and numerical simulations, an explicit expression was derived to decouple the two properties of individual bacteria from the nanoindentation curves. We show that the Young's modulus of bacterial envelope is sensitive to the external osmotic environment, and the turgor pressure is significantly dependent on the external osmotic stress. This method can not only quantify the turgor pressure and envelope elasticity of bacteria, but also help resolve the mechanical behaviors of bacteria in different environments.
细菌的膨压和包膜弹性是两个在细胞变形、分裂和运动中起主导作用的机械参数。然而，由于它们的机制紧密相关，因此对这两个特性的认识还很不清楚。本研究建立了一种纳米压痕法来精确测量活细菌的膨压和包膜弹性。通过原子力显微镜记录了肺炎克雷伯菌的压痕力-深度曲线。通过尺寸分析和数值模拟的结合，推导出了一个显式表达式，将单个细菌的这两个特性从纳米压痕曲线中分离出来。我们表明，细菌包膜的杨氏模量对外界渗透压敏感，膨压显著依赖于外部渗透压。该方法不仅可以定量测量细菌的膨压和包膜弹性，还有助于解析不同环境下细菌的力学行为。
