Stress-mediated growth determines Escherichia coli division site morphogenesis

The bacterial wall is composed of peptidoglycan (PG) and distinguishes bacteria from eukaryotes. Hence, PG synthesis and remodeling are of special interest for the development of antibiotics. Bacterial division represents the most challenging PG remodeling process in the bacterial cell, and its detailed mechanics is not well understood. We propose a simple mechanochemical model that quantitatively reproduces the morphogenesis of the Escherichia coli division site. Its predictions depend on two adjustable parameters associated with the PG recrosslinking dynamics. Changing these parameters also recovers the morphology of divisome mutants, without further adjustments to the model. Moreover, the modifications reflect the expected changes in a rational manner. This indicates that the model captures key aspects of PG remodeling during bacterial division. In order to proliferate, bacteria must remodel their cell wall at the division site. The division process is driven by the enzymatic activity of peptidoglycan synthases and hydrolases around the constricting Z-ring. We introduce a morphoelastic model that correctly reproduces the shape of the division site during the constriction and septation phases of Escherichia coli. In the model, mechanical stress directs the transformation of the bacterial wall. The two constants associated with growth and remodeling respectively are its only adjustable parameters. Different morphologies, corresponding either to mutant or wild type cells, are recovered as a function of the remodeling parameter. In addition, a plausible range for the cell stiffness and turgor pressure was determined by comparing numerical simulations with bacterial cell plasmolysis data.