The outer membrane is an essential load-bearing element in Gram-negative bacteria,Nature

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The outer membrane is an essential load-bearing element in Gram-negative bacteria
Nature ( IF 50.5 ) Pub Date : 2018-07-01 , DOI: 10.1038/s41586-018-0344-3
Enrique R Rojas _{1,

2,

3} , Gabriel Billings ₄ , Pascal D Odermatt _{1,

5} , George K Auer ₆ , Lillian Zhu ₁ , Amanda Miguel ₁ , Fred Chang ₅ , Douglas B Weibel _{6,

7,

8} , Julie A Theriot _{2,

3,

9,

10} , Kerwyn Casey Huang _{1,

3,

10,

11}

Affiliation

Department of Bioengineering, Stanford University, Stanford, CA, USA.
Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA.
Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA.
Department of Physics, Stanford University, Stanford, CA, USA.
Department of Cell and Tissue Biology, University of California San Francisco, San Francisco, CA, USA.
Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA.
Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA.
Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
Howard Hughes Medical Institute, Stanford, CA, USA.
Biophysics Program, Stanford University, Stanford, CA, USA.
Chan Zuckerberg Biohub, San Francisco, CA, USA.

Gram-negative bacteria possess a complex cell envelope that consists of a plasma membrane, a peptidoglycan cell wall and an outer membrane. The envelope is a selective chemical barrier1 that defines cell shape2 and allows the cell to sustain large mechanical loads such as turgor pressure3. It is widely believed that the covalently cross-linked cell wall underpins the mechanical properties of the envelope4,5. Here we show that the stiffness and strength of Escherichia coli cells are largely due to the outer membrane. Compromising the outer membrane, either chemically or genetically, greatly increased deformation of the cell envelope in response to stretching, bending and indentation forces, and induced increased levels of cell lysis upon mechanical perturbation and during L-form proliferation. Both lipopolysaccharides and proteins contributed to the stiffness of the outer membrane. These findings overturn the prevailing dogma that the cell wall is the dominant mechanical element within Gram-negative bacteria, instead demonstrating that the outer membrane can be stiffer than the cell wall, and that mechanical loads are often balanced between these structures.The outer membrane of Gram-negative bacteria is shown to be at least as stiff as the cell wall, and this property enables it to protect cells from mechanical pertubations.

中文翻译：

外膜是革兰氏阴性细菌的重要承载元件

革兰氏阴性细菌拥有复杂的细胞包膜，由质膜、肽聚糖细胞壁和外膜组成。包膜是一种选择性化学屏障1，它定义了细胞形状2，并允许细胞承受较大的机械负载，例如膨胀压力3。人们普遍认为，共价交联的细胞壁支撑着包膜的机械性能4,5。在这里，我们表明大肠杆菌细胞的刚度和强度很大程度上取决于外膜。无论是化学上还是基因上的损害外膜，都会大大增加细胞膜响应拉伸、弯曲和压痕力的变形，并在机械扰动和 L 型增殖过程中诱导细胞裂解水平增加。脂多糖和蛋白质都有助于外膜的硬度。这些发现推翻了普遍存在的教条，即细胞壁是革兰氏阴性细菌内的主要机械元件，而是证明外膜可以比细胞壁更硬，并且机械载荷通常在这些结构之间平衡。革兰氏阴性细菌被证明至少与细胞壁一样坚硬，这种特性使其能够保护细胞免受机械扰动。

更新日期：2018-07-01

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