MreB helical pitch angle determines cell diameter in Escherichia coli

TL;DR

This study reveals that the helical pitch angle of MreB filaments in E. coli determines cell diameter, linking MreB's physical properties to bacterial shape control.

Contribution

It demonstrates that MreB's pitch angle inversely correlates with cell diameter, providing insight into the mechanism of bacterial shape regulation.

Findings

MreB perturbation alters cell diameter over a wide range.

MreB pitch angle inversely correlates with cell diameter.

Other MreB structural features are not significantly correlated.

Abstract

Bacteria have remarkably robust cell shape control mechanisms. For example, cell diameter only varies by a few percent across a population. MreB is necessary for establishment and maintenance of rod shape although the mechanism of shape control remains unknown. We perturbed MreB in two complimentary ways to produce steady-state cell diameters over a wide range, from 790+/-30 nm to 1700+/-20 nm. To determine which properties of MreB are important for diameter control, we correlated structural characteristics of fluorescently-tagged MreB polymers with cell diameter by simultaneously analyzing 3-dimensional images of MreB and cell shape. Our results indicate that the pitch angle of MreB inversely correlates with cell diameter. Other correlations are not found to be significant. These results demonstrate that the physical properties of MreB filaments are important for shape control and support a model in which MreB dictates cell diameter and organizes cell wall growth to produce a chiral cell wall.