Bacterial Cell Division
In bacteria, cell division is carried out by a highly conserved supramolecular complex, the divisome. Understanding the structure and function of the divisome is important for developing new antibiotics. Central to the divisome is a ring-like structure formed by the essential FtsZ protein, named the Z-ring. The Z-ring recruits all other divisome components, and possibly generates a mechanic force to constrict the inner membrane. However, it has been difficult to probe the in vivo structural organization of the Z-ring because of its small size and highly dynamic nature. We made our first major contribution to the field by illustrating the structural organization of the Z-ring in live E. coli cells using single-molecule based superresolution imaging. The structure provides an important foundation to understand how different components of the divisome are assembled and coordinated to carry out cell division. Next, we showed that there exists a multi-layered protein network residing in the cytoplasm, physically connecting the Z-ring to the chromosome to stabilize the Z-ring and coordinate cell division with chromosome segregation. Most importantly, we provide substantial evidence to demonstrate that, in contrary to the common belief, the Z-ring is not the major constrictive force generator. Instead, septum closure rate is limited by cell wall growth, and further modulated by nucleoid segregation. Furthermore, we recently discovered that the Z-ring dynamically treadmills along the division plane. Treadmilling is the apparent movement of a polymer by the continuous polymerization at one end and depolymerization at the other end, with each individual monomer remaining stationery during the process. We found that Z-ring’s treadmilling dynamics is powered by FtsZ’s GTPase activity, and guides the spatiotemporal distribution of cell wall synthesis machineries so that a symmetric, smooth septum and consequently two hemisphere new cell poles could be built in a circular motion. Our work redefines the role of the Z-ring in bacterial cell division, and promotes a new, holistic view of the divisome.
Publications
GTPase activity-coupled treadmilling of the bacterial tubulin FtsZ organizes septal cell wall synthesis. Science. 2017 Feb 17;355(6326):744-747.
Defining the rate-limiting processes of bacterial cytokinesis. Proc Natl Acad Sci U S A. 2016 Feb 23;113(8):E1044-53.
A multi-layered protein network stabilizes the Escherichia coli FtsZ-ring and modulates constriction dynamics. PLoS Genet. 2015 Apr;11(4):e1005128.
In vivo structure of the E. coli FtsZ-ring revealed by photoactivated localization microscopy (PALM). PLoS One. 2010 Sep 13;5(9):e12682.