Single-molecule imaging reveals that Z-ring condensation is essential for cell division in Bacillus subtilis

Although many components of the cell division machinery in bacteria have been identified(1,2), the mechanisms by which they work together to divide the cell remain poorly understood. Key among these components is the tubulin FtsZ, which forms a Z ring at the midcell. FtsZ recruits the other cell division proteins, collectively called the divisome, and the Z ring constricts as the cell divides. We applied live-cell single-molecule imaging to describe the dynamics of the divisome in detail, and to evaluate the individual roles of FtsZ-binding proteins (ZBPs), specifically FtsA and the ZBPs EzrA, SepF and ZapA, in cytokinesis. We show that the divisome comprises two subcomplexes that move differently: stationary ZBPs that transiently bind to treadmilling FtsZ filaments, and a moving complex that includes cell wall synthases. Our imaging analyses reveal that ZBPs bundle FtsZ filaments together and condense them into Z rings, and that this condensation is necessary for cytokinesis.

Automated summary

This study used live-cell single-molecule imaging to reveal that the divisome consists of two subcomplexes, showing that different components move differently. FtsZ-binding proteins were found to play a crucial role in bundling FtsZ filaments together to form Z rings, which are essential for cytokinesis.