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Physical properties of the bacterial outer membrane

Nature Reviews Microbiology volume 20, pages 236–248 (2022)Cite this article

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Abstract

It has long been appreciated that the Gram-negative outer membrane acts as a permeability barrier, but recent studies have uncovered a more expansive and versatile role for the outer membrane in cellular physiology and viability. Owing to recent developments in microfluidics and microscopy, the structural, rheological and mechanical properties of the outer membrane are becoming apparent across multiple scales. In this Review, we discuss experimental and computational studies that have revealed key molecular factors and interactions that give rise to the spatial organization, limited diffusivity and stress-bearing capacity of the outer membrane. These physical properties suggest broad connections between cellular structure and physiology, and we explore future prospects for further elucidation of the implications of outer membrane construction for cellular fitness and survival.

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Fig. 1: The Gram-negative outer membrane composition, and physical and mechanical properties.
Fig. 2: Outer membrane rheology and spatial organization are distinct from those of the peptidoglycan or inner membrane.
Fig. 3: Probing the magnitude and impact of outer membrane stiffness.

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References

  1. Silhavy, T. J., Kahne, D. & Walker, S. The bacterial cell envelope. Cold Spring Harb. Perspect. Biol. 2, a000414 (2010). This review extensively covers the structure, composition, biogenesis and function of the bacterial cell envelopes of Gram-negative and Gram-positive bacteria.

    Article  PubMed  PubMed Central  Google Scholar 

  2. Holtje, J. V. Growth of the stress-bearing and shape-maintaining murein sacculus of Escherichia coli. Microbiol. Mol. Biol. Rev. 62, 181–203 (1998).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  3. Funahara, Y. & Nikaido, H. Asymmetric localization of lipopolysaccharides on the outer membrane of Salmonella typhimurium. J. Bacteriol. 141, 1463–1465 (1980).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  4. Konovalova, A. & Silhavy, T. J. Outer membrane lipoprotein biogenesis: Lol is not the end. Philos. Trans. R. Soc. Lond. B Biol. Sci. 370, 20150030 (2015).

    Article  PubMed  PubMed Central  Google Scholar 

  5. Nikaido, H. Molecular basis of bacterial outer membrane permeability revisited. Microbiol. Mol. Biol. Rev. 67, 593–656 (2003).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  6. Cho, S. H. et al. Detecting envelope stress by monitoring beta-barrel assembly. Cell 159, 1652–1664 (2014).

    Article  CAS  PubMed  Google Scholar 

  7. Konovalova, A., Perlman, D. H., Cowles, C. E. & Silhavy, T. J. Transmembrane domain of surface-exposed outer membrane lipoprotein RcsF is threaded through the lumen of beta-barrel proteins. Proc. Natl Acad. Sci. USA 111, E4350–E4358 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  8. Belas, R. Biofilms, flagella, and mechanosensing of surfaces by bacteria. Trends Microbiol. 22, 517–527 (2014).

    Article  CAS  PubMed  Google Scholar 

  9. Konovalova, A., Mitchell, A. M. & Silhavy, T. J. A lipoprotein/beta-barrel complex monitors lipopolysaccharide integrity transducing information across the outer membrane. eLife 5, e15276 (2016).

    Article  PubMed  PubMed Central  Google Scholar 

  10. Forero, M., Yakovenko, O., Sokurenko, E. V., Thomas, W. E. & Vogel, V. Uncoiling mechanics of Escherichia coli type I fimbriae are optimized for catch bonds. PLoS Biol. 4, e298 (2006).

    Article  PubMed  PubMed Central  Google Scholar 

  11. Kaparakis-Liaskos, M. & Ferrero, R. L. Immune modulation by bacterial outer membrane vesicles. Nat. Rev. Immunol. 15, 375–387 (2015).

    Article  CAS  PubMed  Google Scholar 

  12. Kuehn, M. J. & Kesty, N. C. Bacterial outer membrane vesicles and the host–pathogen interaction. Genes Dev. 19, 2645–2655 (2005).

    Article  CAS  PubMed  Google Scholar 

  13. Giordano, N. P., Cian, M. B. & Dalebroux, Z. D. Outer membrane lipid secretion and the innate immune response to Gram-negative bacteria. Infect. Immun. 88, e00920-19 (2020).

    Article  PubMed  PubMed Central  Google Scholar 

  14. Nudleman, E., Wall, D. & Kaiser, D. Cell-to-cell transfer of bacterial outer membrane lipoproteins. Science 309, 125–127 (2005).

    Article  CAS  PubMed  Google Scholar 

  15. Kulp, A. & Kuehn, M. J. Biological functions and biogenesis of secreted bacterial outer membrane vesicles. Annu. Rev. Microbiol. 64, 163–184 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  16. Nakae, T. & Nikaido, H. Outer membrane as a diffusion barrier in Salmonella typhimurium. Penetration of oligo- and polysaccharides into isolated outer membrane vesicles and cells with degraded peptidoglycan layer. J. Biol. Chem. 250, 7359–7365 (1975). This study examines the penetration of sugars into cell wall-defective cells and outer membrane vesicles and reveals that the outer membrane acts as a size-limiting diffusion barrier.

    Article  CAS  PubMed  Google Scholar 

  17. Nikaido, H. Outer membrane of Salmonella typhimurium. Transmembrane diffusion of some hydrophobic substances. Biochim. Biophys. Acta 433, 118–132 (1976).

    Article  CAS  PubMed  Google Scholar 

  18. Nikaido, H. & Vaara, M. Molecular basis of bacterial outer membrane permeability. Microbiol.Rev. 49, 1 (1985).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  19. Ventola, C. L. The antibiotic resistance crisis: part 1: causes and threats. Pharm. Ther. 40, 277 (2015).

    Google Scholar 

  20. Hofer, U. The cost of antimicrobial resistance. Nat. Rev. Microbiol. 17, 3 (2019).

    Article  CAS  PubMed  Google Scholar 

  21. Lewis, K. Platforms for antibiotic discovery. Nat. Rev. Drug Discov. 12, 371–387 (2013).

    Article  CAS  PubMed  Google Scholar 

  22. Payne, D. J., Gwynn, M. N., Holmes, D. J. & Pompliano, D. L. Drugs for bad bugs: confronting the challenges of antibacterial discovery. Nat. Rev. Drug Discov. 6, 29–40 (2007).

    Article  CAS  PubMed  Google Scholar 

  23. O’Neill, J. Antimicrobial resistance: tackling a crisis for the health and wealth of nations (WHO, 2014).

  24. Zgurskaya, H. I., Lopez, C. A. & Gnanakaran, S. Permeability barrier of Gram-negative cell envelopes and approaches to bypass it. ACS Infect. Dis. 1, 512–522 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  25. Delcour, A. H. Outer membrane permeability and antibiotic resistance. Biochim. Biophys. Acta 1794, 808–816 (2009).

    Article  CAS  PubMed  Google Scholar 

  26. Bentley, A. T. & Klebba, P. E. Effect of lipopolysaccharide structure on reactivity of antiporin monoclonal antibodies with the bacterial cell surface. J. Bacteriol. 170, 1063–1068 (1988).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  27. Storek, K. M. et al. Massive antibody discovery used to probe structure-function relationships of the essential outer membrane protein LptD. eLife 8, e46258 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  28. Storek, K. M. et al. Monoclonal antibody targeting the beta-barrel assembly machine of Escherichia coli is bactericidal. Proc. Natl Acad. Sci. USA 115, 3692–3697 (2018).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  29. Gan, L., Chen, S. & Jensen, G. J. Molecular organization of Gram-negative peptidoglycan. Proc. Natl Acad. Sci. USA 105, 18953–18957 (2008).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  30. Matias, V. R. & Beveridge, T. J. Cryo-electron microscopy reveals native polymeric cell wall structure in Bacillus subtilis 168 and the existence of a periplasmic space. Mol. Microbiol. 56, 240–251 (2005).

    Article  CAS  PubMed  Google Scholar 

  31. Matias, V. R. & Beveridge, T. J. Native cell wall organization shown by cryo-electron microscopy confirms the existence of a periplasmic space in Staphylococcus aureus. J. Bacteriol. 188, 1011–1021 (2006).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  32. Park, J. S. et al. Mechanism of anchoring of OmpA protein to the cell wall peptidoglycan of the Gram-negative bacterial outer membrane. FASEB J. 26, 219–228 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  33. Boags, A. T., Samsudin, F. & Khalid, S. Binding from both sides: TolR and full-length OmpA bind and maintain the local structure of the E. coli cell wall. Structure 27, 713–724 e712 (2019).

    Article  CAS  PubMed  Google Scholar 

  34. Gerding, M. A., Ogata, Y., Pecora, N. D., Niki, H. & de Boer, P. A. The trans-envelope Tol-Pal complex is part of the cell division machinery and required for proper outer-membrane invagination during cell constriction in E. coli. Mol. Microbiol. 63, 1008–1025 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  35. Gray, A. N. et al. Coordination of peptidoglycan synthesis and outer membrane constriction during Escherichia coli cell division. eLife 4, e07118 (2015).

    Article  PubMed Central  Google Scholar 

  36. Paradis-Bleau, C. et al. Lipoprotein cofactors located in the outer membrane activate bacterial cell wall polymerases. Cell 143, 1110–1120 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  37. Typas, A. et al. Regulation of peptidoglycan synthesis by outer-membrane proteins. Cell 143, 1097–1109 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  38. Braun, V. Covalent lipoprotein from the outer membrane of Escherichia coli. Biochim. Biophys. Acta 415, 335–377 (1975).

    Article  CAS  PubMed  Google Scholar 

  39. Deng, Y., Sun, M. & Shaevitz, J. W. Direct measurement of cell wall stress stiffening and turgor pressure in live bacterial cells. Phys. Rev. Lett. 107, 158101 (2011).

    Article  PubMed  Google Scholar 

  40. Rojas, E. R. et al. The outer membrane is an essential load-bearing element in Gram-negative bacteria. Nature 559, 617–621 (2018). Lysis of E. coli cells results in further contraction after hyperosmotic shock-induced plasmolysis, indicating that the outer membrane has stiffness comparable to that of the peptidoglycan cell wall.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  41. Yao, Z., Kahne, D. & Kishony, R. Distinct single-cell morphological dynamics under beta-lactam antibiotics. Mol. Cell 48, 705–712 (2012). This study demonstrates that during treatment of E. coli cells with β-lactam antibiotics, the outer membrane stabilizes bulges formed after cell wall disruption and delays cell lysis.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  42. Young, R. Phage lysis: three steps, three choices, one outcome. J. Microbiol. 52, 243–258 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  43. Jeworrek, C. et al. Effects of specific versus nonspecific ionic interactions on the structure and lateral organization of lipopolysaccharides. Biophys. J. 100, 2169–2177 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  44. Herrmann, M., Schneck, E., Gutsmann, T., Brandenburg, K. & Tanaka, M. Bacterial lipopolysaccharides form physically cross-linked, two-dimensional gels in the presence of divalent cations. Soft Matter 11, 6037–6044 (2015). Rheological measurements of LPS monolayers uncover a viscous-to-elastic transition upon compression that is facilitated by the presence of calcium cations.

    Article  CAS  PubMed  Google Scholar 

  45. Klieneberger, E. The natural occurrence of pleuro-pneumonia-like organisms in apparent symbiosis with Streptobacillus moniliformis and other bacteria. J. Pathol. Bacteriol. 40, 93–105 (1935).

    Article  Google Scholar 

  46. Leaver, M., Dominguez-Cuevas, P., Coxhead, J., Daniel, R. & Errington, J. Life without a wall or division machine in Bacillus subtilis. Nature 457, 849–853 (2009). A strategy is developed to controllably induce the formation of cell wall-free B. subtilis cells, which are found to divide even without the major divisome component FtsZ.

    Article  CAS  PubMed  Google Scholar 

  47. Mercier, R., Kawai, Y. & Errington, J. General principles for the formation and proliferation of a wall-free (L-form) state in bacteria. eLife 3, e04629 (2014).

    Article  PubMed Central  Google Scholar 

  48. Ames, G. F., Spudich, E. N. & Nikaido, H. Protein composition of the outer membrane of Salmonella typhimurium: effect of lipopolysaccharide mutations. J. Bacteriol. 117, 406–416 (1974).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  49. Kamio, Y. & Nikaido, H. Outer membrane of Salmonella typhimurium. Identification of proteins exposed on cell surface. Biochim. Biophys. Acta 464, 589–601 (1977).

    Article  CAS  PubMed  Google Scholar 

  50. Narita, S.-i & Tokuda, H. Bacterial lipoproteins; biogenesis, sorting and quality control. Biochim. Biophys. Acta Mol. Cell Biol. Lipids 1862, 1414–1423 (2017).

    Article  CAS  PubMed  Google Scholar 

  51. Li, G. W., Burkhardt, D., Gross, C. & Weissman, J. S. Quantifying absolute protein synthesis rates reveals principles underlying allocation of cellular resources. Cell 157, 624–635 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  52. Leive, L., Shovlin, V. K. & Mergenhagen, S. E. Physical, chemical, and immunological properties of lipopolysaccharide released from Escherichia coli by ethylenediaminetetraacetate. J. Biol. Chem. 243, 6384–6391 (1968). EDTA treatment of E. coli and Salmonella cells is found to rapidly induce release of a substantial fraction of LPS molecules.

    Article  CAS  PubMed  Google Scholar 

  53. Smit, J., Kamio, Y. & Nikaido, H. Outer membrane of Salmonella typhimurium: chemical analysis and freeze-fracture studies with lipopolysaccharide mutants. J. Bacteriol. 124, 942–958 (1975).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  54. Kamio, Y. & Nikaido, H. Outer membrane of Salmonella typhimurium: accessibility of phospholipid head groups to phospholipase C and cyanogen bromide activated dextran in the external medium. Biochemistry 15, 2561–2570 (1976).

    Article  CAS  PubMed  Google Scholar 

  55. Morrison, D. C. & Jacobs, D. M. Binding of polymyxin B to the lipid A portion of bacterial lipopolysaccharides. Immunochemistry 13, 813–818 (1976).

    Article  CAS  PubMed  Google Scholar 

  56. Nikaido, H., Takeuchi, Y., Ohnishi, S. I. & Nakae, T. Outer membrane of Salmonella typhimurium. Electron spin resonance studies. Biochim. Biophys. Acta 465, 152–164 (1977).

    Article  CAS  PubMed  Google Scholar 

  57. Smit, J. & Nikaido, H. Outer membrane of Gram-negative bacteria. XVIII. Electron microscopic studies on porin insertion sites and growth of cell surface of Salmonella typhimurium. J. Bacteriol. 135, 687–702 (1978).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  58. Boyd, A. & Holland, I. B. Regulation of the synthesis of surface protein in the cell cycle of E. coli B/r. Cell 18, 287–296 (1979).

    Article  CAS  PubMed  Google Scholar 

  59. Raetz, C. R. & Whitfield, C. Lipopolysaccharide endotoxins. Annu. Rev. Biochem. 71, 635–700 (2002).

    Article  CAS  PubMed  Google Scholar 

  60. Hancock, R. E. W. & Bell, A. in Perspectives in Antiinfective Therapy (eds Jackson, G. G., Schlumberger, H. D. & Zeiler, J.-J.) 42–53 (Springer, 1988).

  61. Srimal, S., Surolia, N., Balasubramanian, S. & Surolia, A. Titration calorimetric studies to elucidate the specificity of the interactions of polymyxin B with lipopolysaccharides and lipid A. Biochem. J. 315, 679–686 (1996).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  62. Jarosławski, S., Duquesne, K., Sturgis, J. N. & Scheuring, S. High-resolution architecture of the outer membrane of the Gram-negative bacteria Roseobacter denitrificans. Mol. Microbiol. 74, 1211–1222 (2009).

    Article  PubMed  Google Scholar 

  63. Qiao, S., Luo, Q., Zhao, Y., Zhang, X. C. & Huang, Y. Structural basis for lipopolysaccharide insertion in the bacterial outer membrane. Nature 511, 108–111 (2014). The crystal structure is solved for the protein complex LptD–LptE, which is responsible for the insertion of LPS molecules into the outer membrane, revealing a plug-and-barrel architecture that enables diffusion of LPS molecules into the outer membrane.

    Article  CAS  PubMed  Google Scholar 

  64. Arunmanee, W. et al. Gram-negative trimeric porins have specific LPS binding sites that are essential for porin biogenesis. Proc. Natl Acad. Sci. USA 113, E5034–E5043 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  65. Casuso, I. et al. Characterization of the motion of membrane proteins using high-speed atomic force microscopy. Nat. Nanotechnol. 7, 525–529 (2012). High-speed AFM reveals that the distribution of the outer membrane protein OmpF across the cell surface is a result of diffusion-limited aggregation and that protein–protein interactions can trap freely diffusing proteins.

    Article  CAS  PubMed  Google Scholar 

  66. Yamashita, H. et al. Single-molecule imaging on living bacterial cell surface by high-speed AFM. J. Mol. Biol. 422, 300–309 (2012).

    Article  CAS  PubMed  Google Scholar 

  67. Chavent, M. et al. How nanoscale protein interactions determine the mesoscale dynamic organisation of bacterial outer membrane proteins. Nat. Commun. 9, 2846 (2018).

    Article  PubMed  PubMed Central  Google Scholar 

  68. Konovalova, A., Kahne, D. E. & Silhavy, T. J. Outer membrane biogenesis. Annu. Rev. Microbiol. 71, 539–556 (2017).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  69. Okuda, S., Sherman, D. J., Silhavy, T. J., Ruiz, N. & Kahne, D. Lipopolysaccharide transport and assembly at the outer membrane: the PEZ model. Nat. Rev. Microbiol. 14, 337–345 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  70. Patel, D. S., Qi, Y. & Im, W. Modeling and simulation of bacterial outer membranes and interactions with membrane proteins. Curr. Opin. Struct. Biol. 43, 131–140 (2017).

    Article  CAS  PubMed  Google Scholar 

  71. Im, W. & Khalid, S. Molecular simulations of Gram-negative bacterial membranes come of age. Annu. Rev. Phys. Chem. 71, 171–188 (2020). This review discusses recent progress in and challenges for computational simulations of the inner and outer membranes and the periplasm, with an emphasis on molecular interactions and the spatial organization of membrane structures.

    Article  CAS  PubMed  Google Scholar 

  72. Gao, Y., Lee, J., Widmalm, G. & Im, W. Modeling and simulation of bacterial outer membranes with lipopolysaccharides and enterobacterial common antigens. J. Phys. Chem. B 124, 5948–5956 (2020).

    Article  CAS  PubMed  Google Scholar 

  73. Nascimento, A. Jr, Pontes, F. J., Lins, R. D. & Soares, T. A. Hydration, ionic valence and cross-linking propensities of cations determine the stability of lipopolysaccharide (LPS) membranes. Chem. Commun. 50, 231–233 (2014).

    Article  CAS  Google Scholar 

  74. Patel, D. S. et al. Dynamics and interactions of OmpF and LPS: influence on pore accessibility and ion permeability. Biophys. J. 110, 930–938 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  75. Domínguez-Medina, C. C. et al. Outer membrane protein size and LPS O-antigen define protective antibody targeting to the Salmonella surface. Nat. Commun. 11, 1–11 (2020).

    Article  Google Scholar 

  76. Kortright, K. E., Chan, B. K. & Turner, P. E. High-throughput discovery of phage receptors using transposon insertion sequencing of bacteria. Proc. Natl Acad. Sci. USA 117, 18670–18679 (2020).

    Article  PubMed  PubMed Central  Google Scholar 

  77. Fleming, T. C. et al. Dynamic SpoIIIE assembly mediates septal membrane fission during Bacillus subtilis sporulation. Genes Dev. 24, 1160–1172 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  78. de Pedro, M. A., Grunfelder, C. G. & Schwarz, H. Restricted mobility of cell surface proteins in the polar regions of Escherichia coli. J. Bacteriol. 186, 2594–2602 (2004). Pulse–chase experiments with growing E. coli cells result in localization of fluorescently labelled surface proteins mostly at the cell poles, indicating that some of the proteins have limited mobility and that the poles are more inert than the cylindrical regions.

    Article  PubMed  PubMed Central  Google Scholar 

  79. Ghosh, A. S. & Young, K. D. Helical disposition of proteins and lipopolysaccharide in the outer membrane of Escherichia coli. J. Bacteriol. 187, 1913–1922 (2005).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  80. Ursell, T. S., Trepagnier, E. H., Huang, K. C. & Theriot, J. A. Analysis of surface protein expression reveals the growth pattern of the Gram-negative outer membrane. PLoS Comput. Biol. 8, e1002680 (2012). Tracking of newly synthesized LamB reveals that this porin is inserted into the outer membrane in discrete puncta, which move apart owing to cell growth and become relatively stationary at the poles, highlighting the limited mobility of LamB.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  81. Rassam, P. et al. Supramolecular assemblies underpin turnover of outer membrane proteins in bacteria. Nature 523, 333–336 (2015). This study of E. coli cells shows that several outer membrane proteins form cellular-scale clusters containing the β-barrel assembly machine complex, which catalyses the insertion of new proteins into the outer membrane, and that insertion happens mostly frequently in the cylindrical region, pushing old protein islands towards the poles.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  82. Koch, A. L. & Woldringh, C. L. The metabolic inertness of the pole wall of a Gram-negative rod. J. Theor. Biol. 171, 415–425 (1994).

    Article  CAS  Google Scholar 

  83. De Pedro, M., Quintela, J. C., Höltje, J. & Schwarz, H. Murein segregation in Escherichia coli. J. Bacteriol. 179, 2823–2834 (1997).

    Article  PubMed  PubMed Central  Google Scholar 

  84. Ursell, T. S. et al. Rod-like bacterial shape is maintained by feedback between cell curvature and cytoskeletal localization. Proc. Natl Acad. Sci. USA 111, E1025–E1034 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  85. Brown, P. J. et al. Polar growth in the alphaproteobacterial order Rhizobiales. Proc. Natl Acad. Sci. USA 109, 1697–1701 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  86. Steinhauer, J., Agha, R., Pham, T., Varga, A. W. & Goldberg, M. B. The unipolar Shigella surface protein IcsA is targeted directly to the bacterial old pole: IcsP cleavage of IcsA occurs over the entire bacterial surface. Mol. Microbiol. 32, 367–377 (1999).

    Article  CAS  PubMed  Google Scholar 

  87. Charles, M., Perez, M., Kobil, J. H. & Goldberg, M. B. Polar targeting of Shigella virulence factor IcsA in Enterobacteriacae and Vibrio. Proc. Natl Acad. Sci. USA 98, 9871–9876 (2001).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  88. Cowles, C. E., Li, Y., Semmelhack, M. F., Cristea, I. M. & Silhavy, T. J. The free and bound forms of Lpp occupy distinct subcellular locations in Escherichia coli. Mol. Microbiol. 79, 1168–1181 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  89. Winkle, M. et al. DpaA detaches Braun’s lipoprotein from peptidoglycan. mBio 12, e00836-21 (2021).

    Article  PubMed  PubMed Central  Google Scholar 

  90. Bahadur, R., Chodisetti, P. K. & Reddy, M. Cleavage of Braun’s lipoprotein Lpp from the bacterial peptidoglycan by a paralog of l,d-transpeptidases, LdtF. Proc. Natl Acad. Sci. USA 118, e2101989118 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  91. Rothenberg, E. et al. Single-virus tracking reveals a spatial receptor-dependent search mechanism. Biophys. J. 100, 2875–2882 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  92. Lessen, H. J., Fleming, P. J., Fleming, K. G. & Sodt, A. J. Building blocks of the outer membrane: calculating a general elastic energy model for beta-barrel membrane proteins. J. Chem. Theory Comput. 14, 4487–4497 (2018).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  93. Kleanthous, C., Rassam, P. & Baumann, C. G. Protein–protein interactions and the spatiotemporal dynamics of bacterial outer membrane proteins. Curr. Opin. Struct. Biol. 35, 109–115 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  94. Asmar, A. T. et al. Communication across the bacterial cell envelope depends on the size of the periplasm. PLoS Biol. 15, e2004303 (2017).

    Article  PubMed  PubMed Central  Google Scholar 

  95. Mathelie-Guinlet, M., Asmar, A. T., Collet, J. F. & Dufrene, Y. F. Lipoprotein Lpp regulates the mechanical properties of the E. coli cell envelope. Nat. Commun. 11, 1789 (2020). With use of AFM, the lipoprotein Lpp was found to affect the dimensions and the mechanical stiffness of E. coli cells.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  96. Godessart, P. et al. β-Barrels covalently link peptidoglycan and the outer membrane in the α-proteobacterium Brucella abortus. Nat. Microbiol. 6, 27–33 (2020).

    Article  PubMed  Google Scholar 

  97. Sandoz, K. M. et al. β-Barrel proteins tether the outer membrane in many Gram-negative bacteria. Nat. Microbiol. 195, 213–219 (2020).

    Google Scholar 

  98. Berry, J., Rajaure, M., Pang, T. & Young, R. The spanin complex is essential for lambda lysis. J. Bacteriol. 194, 5667–5674 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  99. Huang, K. C., Mukhopadhyay, R., Wen, B., Gitai, Z. & Wingreen, N. S. Cell shape and cell-wall organization in Gram-negative bacteria. Proc. Natl Acad. Sci. USA 105, 19282–19287 (2008).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  100. Billings, G. et al. De novo morphogenesis in L-forms via geometric control of cell growth. Mol. Microbiol. 93, 883–896 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  101. Kawai, Y. et al. Cell growth of wall-free L-form bacteria is limited by oxidative damage. Curr. Biol. 25, 1613–1618 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  102. Ranjit, D. K. & Young, K. D. The Rcs stress response and accessory envelope proteins are required for de novo generation of cell shape in Escherichia coli. J. Bacteriol. 195, 2452–2462 (2013).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  103. Hwang, H., Paracini, N., Parks, J. M., Lakey, J. H. & Gumbart, J. C. Distribution of mechanical stress in the Escherichia coli cell envelope. Biochim. Biophys. Acta Biomembr. 1860, 2566–2575 (2018).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  104. Amir, A., Babaeipour, F., McIntosh, D. B., Nelson, D. R. & Jun, S. Bending forces plastically deform growing bacterial cell walls. Proc. Natl Acad. Sci. USA 111, 5778–5783 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  105. Ruiz, N., Wu, T., Kahne, D. & Silhavy, T. J. Probing the barrier function of the outer membrane with chemical conditionality. ACS Chem. Biol. 1, 385–395 (2006). Chemical conditionality exploiting the bile acid sensitivity of an E. coli mutant with a compromised outer membrane selects for a suppressor in bamA, an essential gene involved in the biogenesis of OMPs.

    Article  CAS  PubMed  Google Scholar 

  106. Mitchell, A. M., Srikumar, T. & Silhavy, T. J. Cyclic enterobacterial common antigen maintains the outer membrane permeability barrier of Escherichia coli in a manner controlled by YhdP. mBio 9, e01321-18 (2018).

    Article  PubMed  PubMed Central  Google Scholar 

  107. Grimm, J. et al. The inner membrane protein YhdP modulates the rate of anterograde phospholipid flow in Escherichia coli. Proc. Natl Acad. Sci. USA 117, 26907–26914 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  108. Tropini, C. et al. Principles of bacterial cell-size determination revealed by cell-wall synthesis perturbations. Cell Rep. 9, 1520–1527 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  109. Goodell, E. W., Lopez, R. & Tomasz, A. Suppression of lytic effect of beta lactams on Escherichia coli and other bacteria. Proc. Natl Acad. Sci. USA 73, 3293–3297 (1976).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  110. Rajaure, M., Berry, J., Kongari, R., Cahill, J. & Young, R. Membrane fusion during phage lysis. Proc. Natl Acad. Sci. USA 112, 5497–5502 (2015). Fusion of the cytoplasmic membrane and the outer membrane, which serves as the last step in phage-induced cell lysis, is found to be mediated by the phage-encoded protein spanin.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  111. Berry, J., Summer, E. J., Struck, D. K. & Young, R. The final step in the phage infection cycle: the Rz and Rz1 lysis proteins link the inner and outer membranes. Mol. Microbiol. 70, 341–351 (2008).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  112. Chowdhury, N., Marschner, P. & Burns, R. G. Soil microbial activity and community composition: impact of changes in matric and osmotic potential. Soil. Biol. Biochem. 43, 1229–1236 (2011).

    Article  CAS  Google Scholar 

  113. Shiau, Y. F., Feldman, G. M., Resnick, M. A. & Coff, P. M. Stool electrolyte and osmolality measurements in the evaluation of diarrheal disorders. Ann. Intern. Med. 102, 773–775 (1985).

    Article  CAS  PubMed  Google Scholar 

  114. Cox, A. D. et al. Phosphorylation of the lipid A region of meningococcal lipopolysaccharide: identification of a family of transferases that add phosphoethanolamine to lipopolysaccharide. J. Bacteriol. 185, 3270–3277 (2003).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  115. Simpson, B. W. & Trent, M. S. Pushing the envelope: LPS modifications and their consequences. Nat. Rev. Microbiol. 17, 403–416 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  116. Martynowycz, M. W. et al. Salmonella membrane structural remodeling increases resistance to antimicrobial peptide LL-37. ACS Infect. Dis. 5, 1214–1222 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  117. Alphen, W. V. & Lugtenberg, B. Influence of osmolarity of the growth medium on the outer membrane protein pattern of Escherichia coli. J. Bacteriol. 131, 623–630 (1977).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  118. Lugtenberg, B., Peters, R., Bernheimer, H. & Berendsen, W. Influence of cultural conditions and mutations on the composition of the outer membrane proteins of Escherichia coli. Mol. Gen. Genet. 147, 251–262 (1976).

    Article  CAS  PubMed  Google Scholar 

  119. Morein, S., Andersson, A., Rilfors, L. & Lindblom, G. Wild-type Escherichia coli cells regulate the membrane lipid composition in a “window” between gel and non-lamellar structures. J. Biol. Chem. 271, 6801–6809 (1996).

    Article  CAS  PubMed  Google Scholar 

  120. Sanders, C. R. & Mittendorf, K. F. Tolerance to changes in membrane lipid composition as a selected trait of membrane proteins. Biochemistry 50, 7858–7867 (2011).

    Article  CAS  PubMed  Google Scholar 

  121. Stokes, J. M. et al. Cold stress makes Escherichia coli susceptible to glycopeptide antibiotics by altering outer membrane integrity. Cell Chem. Biol. 23, 267–277 (2016).

    Article  CAS  PubMed  Google Scholar 

  122. Budin, I. et al. Viscous control of cellular respiration by membrane lipid composition. Science 362, 1186–1189 (2018).

    Article  CAS  PubMed  Google Scholar 

  123. Nichol, C. P., Davis, J. H., Weeks, G. & Bloom, M. Quantitative study of the fluidity of Escherichia coli membranes using deuterium magnetic resonance. Biochemistry 19, 451–457 (1980).

    Article  CAS  PubMed  Google Scholar 

  124. Carty, S. M., Sreekumar, K. R. & Raetz, C. R. Effect of cold shock on lipid A biosynthesis in Escherichia coli: induction at 12°C of an acyltransferase specific for palmitoleoyl-acyl carrier protein. J. Biol. Chem. 274, 9677–9685 (1999).

    Article  CAS  PubMed  Google Scholar 

  125. Vorachek-Warren, M. K., Carty, S. M., Lin, S., Cotter, R. J. & Raetz, C. R. An Escherichia coli mutant lacking the cold shock-induced palmitoleoyltransferase of lipid A biosynthesis: absence of unsaturated acyl chains and antibiotic hypersensitivity at 12°C. J. Biol. Chem. 277, 14186–14193 (2002).

    Article  CAS  PubMed  Google Scholar 

  126. Kumada, H., Haishima, Y., Umemoto, T. & Tanamoto, K. Structural study on the free lipid A isolated from lipopolysaccharide of Porphyromonas gingivalis. J. Bacteriol. 177, 2098–2106 (1995).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  127. Reife, R. A. et al. Porphyromonas gingivalis lipopolysaccharide lipid A heterogeneity: differential activities of tetra-and penta-acylated lipid A structures on E-selectin expression and TLR4 recognition. Cell. Microbiol. 8, 857–868 (2006).

    Article  CAS  PubMed  Google Scholar 

  128. Mitchell, A. M., Wang, W. & Silhavy, T. J. Novel RpoS-dependent mechanisms strengthen the envelope permeability barrier during stationary phase. J. Bacteriol. 199, e00708-16 (2017).

    Article  PubMed  Google Scholar 

  129. Kellenberger, E. The ‘Bayer bridges’ confronted with results from improved electron microscopy methods. Mol. Microbiol. 4, 697–705 (1990).

    Article  CAS  PubMed  Google Scholar 

  130. Bayer, M. Areas of adhesion between wall and membrane of Escherichia coli. Microbiology 53, 395–404 (1968).

    CAS  Google Scholar 

  131. Coudray, N. et al. Structure of bacterial phospholipid transporter MlaFEDB with substrate bound. eLife 9, e62518 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  132. Ekiert, D. C. et al. Architectures of lipid transport systems for the bacterial outer membrane. Cell 169, 273–285. e217 (2017).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  133. Isom, G. L. et al. LetB structure reveals a tunnel for lipid transport across the bacterial envelope. Cell 181, 653–664 e619 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  134. Alvira, S. et al. Inter-membrane association of the Sec and BAM translocons for bacterial outer-membrane biogenesis. eLife 9, e60669 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  135. Proseus, T. E. & Boyer, J. S. Calcium pectate chemistry causes growth to be stored in Chara corallina: a test of the pectate cycle. Plant. Cell Env. 31, 1147–1155 (2008).

    Article  CAS  Google Scholar 

  136. Chen, P. et al. Nanoscale probing the kinetics of oriented bacterial cell growth using atomic force microscopy. Small 10, 3018–3025 (2014).

    Article  CAS  PubMed  Google Scholar 

  137. Cayley, D. S., Guttman, H. J. & Record, M. T. Jr Biophysical characterization of changes in amounts and activity of Escherichia coli cell and compartment water and turgor pressure in response to osmotic stress. Biophys. J. 78, 1748–1764 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  138. Schirner, K., Marles-Wright, J., Lewis, R. J. & Errington, J. Distinct and essential morphogenic functions for wall- and lipo-teichoic acids in Bacillus subtilis. EMBO J. 28, 830–842 (2009).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  139. Kern, T. et al. Dynamics characterization of fully hydrated bacterial cell walls by solid-state NMR: evidence for cooperative binding of metal ions. J. Am. Chem. Soc. 132, 10911–10919 (2010).

    Article  CAS  PubMed  Google Scholar 

  140. Rojas, E. R., Huang, K. C. & Theriot, J. A. Homeostatic cell growth is accomplished mechanically through membrane tension inhibition of cell-wall synthesis. Cell Syst. 5, 578–590 e576 (2017).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  141. Martens, E. C., Roth, R., Heuser, J. E. & Gordon, J. I. Coordinate regulation of glycan degradation and polysaccharide capsule biosynthesis by a prominent human gut symbiont. J. Biol. Chem. 284, 18445–18457 (2009).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  142. Bharat, T. A. et al. Structure of the hexagonal surface layer on Caulobacter crescentus cells. Nat. Microbiol. 2, 1–6 (2017).

    Article  Google Scholar 

  143. Comerci, C. J. et al. Topologically-guided continuous protein crystallization controls bacterial surface layer self-assembly. Nat. Commun. 10, 1–10 (2019).

    Article  CAS  Google Scholar 

  144. Herrmann, J. et al. Environmental calcium controls alternate physical states of the Caulobacter surface layer. Biophys. J. 112, 1841–1851 (2017).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  145. Auer, G. K. et al. Mechanical genomics identifies diverse modulators of bacterial cell stiffness. Cell Syst. 2, 402–411 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  146. Tuson, H. H. et al. Measuring the stiffness of bacterial cells from growth rates in hydrogels of tunable elasticity. Mol. Microbiol. 84, 874–891 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  147. Hughes, A. V. et al. Physical properties of bacterial outer membrane models: neutron reflectometry & molecular simulation. Biophys. J. 116, 1095–1104 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  148. Vadillo-Rodriguez, V., Beveridge, T. J. & Dutcher, J. R. Surface viscoelasticity of individual Gram-negative bacterial cells measured using atomic force microscopy. J. Bacteriol. 190, 4225–4232 (2008).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

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Acknowledgements

The authors thank the members of the Huang, Rutherford and Silhavy laboratories for helpful discussions. The authors acknowledge support from the Allen Discovery Center at Stanford University (to K.C.H.) and US National Institute of General Medical Sciences grants R35 GM118024 (to T.J.S.) and RM1 GM135102 (to K.C.H.). K.C.H. is a Chan Zuckerberg Biohub Investigator.

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Authors and Affiliations

  1. Department of Bioengineering, Stanford University, Stanford, CA, USA

    Jiawei Sun & Kerwyn Casey Huang

  2. Department of Infectious Diseases, Genentech Inc., South San Francisco, CA, USA

    Steven T. Rutherford

  3. Department of Molecular Biology, Princeton University, Princeton, NJ, USA

    Thomas J. Silhavy

  4. Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA

    Kerwyn Casey Huang

  5. Chan Zuckerberg Biohub, San Francisco, CA, USA

    Kerwyn Casey Huang

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  1. Jiawei Sun
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The authors contributed equally to all aspects of the article.

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Sun, J., Rutherford, S.T., Silhavy, T.J. et al. Physical properties of the bacterial outer membrane. Nat Rev Microbiol 20, 236–248 (2022). https://doi.org/10.1038/s41579-021-00638-0

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