Shape dynamics of growing cell walls

TL;DR

This paper presents a theoretical framework for understanding the shape dynamics of growing bacterial cell walls, linking growth, shape, and division through energy and mechanical constraints.

Contribution

It introduces a novel physical model that connects cell wall energy, shape evolution, and growth processes in bacteria with various morphologies.

Findings

Exponential growth requires constant energy dissipation per volume.

Different bacterial shapes influence growth and constriction dynamics.

Shape transformation during division is predicted to be discontinuous.

Abstract

We introduce a general theoretical framework to study the shape dynamics of actively growing and remodeling surfaces. Using this framework we develop a physical model for growing bacterial cell walls and study the interplay of cell shape with the dynamics of growth and constriction. The model allows us to derive constraints on cell wall mechanical energy based on the observed dynamics of cell shape. We predict that exponential growth in cell size requires a constant amount of cell wall energy to be dissipated per unit volume. We use the model to understand and contrast growth in bacteria with different shapes such as spherical, ellipsoidal, cylindrical and toroidal morphologies. Coupling growth to cell wall constriction, we predict a discontinuous shape transformation, from partial constriction to cell division, as a function of the chemical potential driving cell-wall synthesis. Our model for cell wall energy and shape dynamics relates growth kinetics with cell geometry, and provides a unified framework to describe the interplay between shape, growth and division in bacterial cells.