A model of cell-wall dynamics during sporulation in Bacillus subtilis

TL;DR

This paper presents a biophysical model explaining the force mechanisms behind cell-wall remodeling during Bacillus subtilis sporulation, highlighting the roles of line tension, pressure imbalance, and growth constraints.

Contribution

It introduces a novel biophysical model for cell-wall dynamics during sporulation, integrating forces and predicting key factors influencing engulfment.

Findings

Line tension from septum attachment promotes sporulation.

Imbalance in turgor pressures facilitates engulfment.

Mother-cell growth can hinder the process.

Abstract

To survive starvation, Bacillus subtilis forms durable spores. After asymmetric cell division, the septum grows around the forespore in a process called engulfment, but the mechanism of force generation is unknown. Here, we derived a novel biophysical model for the dynamics of cell-wall remodeling during engulfment based on a balancing of dissipative, active, and mechanical forces. By plotting phase diagrams, we predict that sporulation is promoted by a line tension from the attachment of the septum to the outer cell wall, as well as by an imbalance in turgor pressures in the mother-cell and forespore compartments. We also predict that significant mother-cell growth hinders engulfment. Hence, relatively simple physical principles may guide this complex biological process.