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

• Published in: Nature (London) Vol. 559; no. 7715; pp. 617 - 621
• Main Authors: Rojas, Enrique R, Billings, Gabriel, Odermatt, Pascal D, Auer, George K, Zhu, Lillian, Miguel, Amanda, Chang, Fred, Weibel, Douglas B, Theriot, Julie A, Huang, Kerwyn Casey
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.07.2018
• Subjects: Antibiotics; Bacteria; Cell envelopes; Cell Membrane - drug effects; Cell Membrane - metabolism; Cell membranes; Cell Wall - drug effects; Cell Wall - metabolism; Chromatography; Crosslinking; Deformation; Detergents - pharmacology; E coli; Escherichia coli; Escherichia coli - cytology; Escherichia coli - drug effects; Escherichia coli - metabolism; Gram-negative bacteria; Gram-Negative Bacteria - cytology; Gram-Negative Bacteria - drug effects; Gram-Negative Bacteria - metabolism; Indentation; Lipopolysaccharides; Load bearing elements; Lysis; Mechanical properties; Microbial Viability - drug effects; Morphogenesis; Organic chemistry; Outer membranes; Peptidoglycans; Permeability; Properties; Proteins; Stiffness; Turgor; Weight-Bearing; United States > US
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-018-0344-3

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 barrier that defines cell shape and allows the cell to sustain large mechanical loads such as turgor pressure . It is widely believed that the covalently cross-linked cell wall underpins the mechanical properties of the envelope . 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.