Z-ring dynamics in Escherichia coli

by Anindita Dutta

Department of Physics, BGU

at Biological and soft-matter physics

Thu, 31 Mar 2022, 12:00
Sacta-Rashi Building for Physics (54), room 207

Abstract

Bacterial cell division has been extensively studied for many years, especially for rod-shaped Escherichia coli. The FtsZ protein is a principal component of the cell division machinery, the divisome, as it coordinates the assembly of the proteins involved in septum wall synthesis necessary to ensure successful cell septation. During division, FtsZ polymerizes on the cytoplasmic face of the inner cell membrane to form a ring-like structure, the Z-ring, at the mid-cell region and recruits more than 30 different proteins to the division site. The current perception of the Z-ring is that of a rotating structure resulting from the treadmilling of its FtsZ filaments. Elements of this structure are highly dynamic and its motion correlates with the dynamics of the peptidoglycan synthesizing enzymes contained in the divisome. In slow growing cells, the Z-ring was shown to be highly inhomogeneous. Therefore, it remains an open question as to how this dynamic Z-ring is associated with septum formation and how it leads to the emergence of symmetric constriction. We address this question by tracking FtsZ clusters on the Z-ring of vertically aligned live E. coli cells embedded in agarose. The agarose embedded cells are observed in three different series of experiments. First, we investigate whether the rotation of the FtsZ polymers on the Z-ring exhibits a preferred direction relative to the orientation of the newly formed pole. Next, we study the dynamics of the FtsZ polymers on the Z-ring at different stages of the cell cycle. Finally, we explore the behavior of the FtsZ tracks along the Z-ring on long time scales that are of the same order as the division time. We find that the dynamics of the FtsZ clusters are much more complex than previously believed and their motion may be classified as either directed, diffusive, or localized. The simplest model of septation whereby the FtsZ clusters exhibiting directed motion are dragging along septal wall-building machinery is found to strongly underestimate the rate of constriction. This suggests that the clusters that either diffuse or are localized may also contribute to the septal wall formation in ways that remain to be explored.

Created on 28-03-2022 by Feingold, Mario (mario)
Updaded on 28-03-2022 by Feingold, Mario (mario)