title: Coarse-grained simulations of bacterial cell wall growth reveal that local coordination alone can be sufficient to maintain rod shape.
abstract: Bacteria are surrounded by a peptidoglycan (PG) cell wall that must be remodeled to allow cell growth. While many structural details and properties of PG and the individual enzymes involved are known, how the process is coordinated to maintain cell integrity and rod shape is not understood. We have developed a coarse-grained method to simulate how individual transglycosylases, transpeptidases, and endopeptidases could introduce new material into an existing unilayer PG network. We find that a simple model with no enzyme coordination fails to maintain cell wall integrity and rod shape. We then iteratively analyze failure modes and explore different mechanistic hypotheses about how each problem might be overcome by the macromolecules involved. In contrast to a current theory, which posits that long MreB filaments are needed to coordinate PG insertion sites, we find that local coordination of enzyme activities in individual complexes can be sufficient to maintain cell integrity and rod shape. We also present possible molecular explanations for the existence of monofunctional transpeptidases and glycosidases (glycoside hydrolases), trimeric peptide crosslinks, cell twisting during growth, and synthesis of new strands in pairs.
authors.affiliation: Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125;
authors.forename: Lam T
authors.initials: LT
authors.lastname: Nguyen
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, GA 30332;
authors.forename: James C
authors.initials: JC
authors.lastname: Gumbart
authors.affiliation: Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Morgan
authors.initials: M
authors.lastname: Beeby
authors.affiliation: Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125; jensen@caltech.edu.
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Jensen
mesh_terms: D001419:Bacteria / Q000201:enzymology / Q000254:growth & development*; D048430:Cell Shape; D002473:Cell Wall / Q000502:physiology*; D006031:Glycosylation; D006868:Hydrolysis; D010447:Peptide Hydrolases / Q000378:metabolism; D046928:Peptidoglycan Glycosyltransferase / Q000378:metabolism
chemical_list: D046928:Peptidoglycan Glycosyltransferase; D010447:Peptide Hydrolases
keywords: cell wall synthesis; coarse-grained modeling; morphogenesis