RodZ promotes MreB polymer formation and curvature localization to determine the cylindrical uniformity of E. coli shape

Cell shape in bacteria is determined by the cell wall, which is synthesized by a variety of proteins whose actions are coordinated by the actin-like MreB protein. MreB uses local geometric cues of envelope curvature to avoid the cell poles and localize to specific regions of the cell body. However, it remains unclear whether MreBs curvature preference is regulated by additional factors, and which features of MreB are essential for specific aspects of rod shape growth, such as cylindrical uniformity. Here we show that in addition to its previously-described role in mediating MreB motion, RodZ also modulates MreB polymer number and curvature preference. MreB polymer number and curvature localization can be regulated independently. Quantitative 3D measurements and a series of mutant strains show that among various properties of MreB, polymer number, total length of MreB polymers, and MreB curvature preference are the key determinants of cylindrical uniformity, a measure of the variability in radius within a single cell. Changes in the values of these parameters are highly predictive of the resulting changes in cell shape (r2=0.93). Our data suggest a model for rod shape in which RodZ promotes the assembly of multiple long MreB polymers that ensure the growth of a uniform cylinder.