title: Escherichia coli peptidoglycan structure and mechanics as predicted by atomic-scale simulations.
abstract: Bacteria face the challenging requirement to maintain their shape and avoid rupture due to the high internal turgor pressure, but simultaneously permit the import and export of nutrients, chemical signals, and virulence factors. The bacterial cell wall, a mesh-like structure composed of cross-linked strands of peptidoglycan, fulfills both needs by being semi-rigid, yet sufficiently porous to allow diffusion through it. How the mechanical properties of the cell wall are determined by the molecular features and the spatial arrangement of the relatively thin strands in the larger cellular-scale structure is not known. To examine this issue, we have developed and simulated atomic-scale models of Escherichia coli cell walls in a disordered circumferential arrangement. The cell-wall models are found to possess an anisotropic elasticity, as known experimentally, arising from the orthogonal orientation of the glycan strands and of the peptide cross-links. Other features such as thickness, pore size, and disorder are also found to generally agree with experiments, further supporting the disordered circumferential model of peptidoglycan. The validated constructs illustrate how mesoscopic structure and behavior emerge naturally from the underlying atomic-scale properties and, furthermore, demonstrate the ability of all-atom simulations to reproduce a range of macroscopic observables for extended polymer meshes.
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia, United States of America.
authors.forename: James C
authors.initials: JC
authors.lastname: Gumbart
authors.affiliation: Imperial College London, South Kensington Campus, London, United Kingdom.
authors.forename: Morgan
authors.initials: M
authors.lastname: Beeby
authors.affiliation: California Institute of Technology and Howard Hughes Medical Institute, Pasadena, California, United States of America.
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Jensen
authors.affiliation: Department of Biochemistry and Molecular Biology and Gordon Center for Integrative Science, The University of Chicago, Chicago, Illinois, United States of America.
authors.forename: Benoît
authors.initials: B
authors.lastname: Roux
mesh_terms: D055592:Biophysical Phenomena; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D019295:Computational Biology; D003198:Computer Simulation; D004926:Escherichia coli / Q000737:chemistry* / Q000502:physiology; D008958:Models, Molecular; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D010457:Peptidoglycan / Q000737:chemistry* / Q000378:metabolism
chemical_list: D010457:Peptidoglycan