Divisomes

Divisomes are multiprotein complexes in bacteria that govern cytokinesis, assembling at the future division site to coordinate the invagination of the cytoplasmic membrane and the synthesis of septal peptidoglycan. In many bacteria, including Escherichia coli, the core of the divisome centers on FtsZ, a tubulin homolog that polymerizes into a Z-ring at midcell and is anchored to the inner membrane by FtsA and ZipA.

The divisome assembles in stages. The FtsZ ring acts as a scaffold to recruit early division proteins and, subsequently, late components such as FtsK, FtsQ, FtsL, FtsB, FtsW, FtsI (PBP3), and FtsN. FtsW and FtsI synthesize septal peptidoglycan, while FtsN comes in to trigger final constriction. Site selection is regulated by systems such as MinCDE and nucleoid occlusion factors (Noc in some Gram-positives or SlmA in others), which prevent division over unsegregated chromosomes and bias the division site to midcell.

Functionally, the divisome couples membrane invagination with cell wall remodeling, coordinating mechanical constriction with enzymatic synthesis of the septum. Energy for the process arises from GTP hydrolysis by FtsZ and the activity of the peptidoglycan synthesis enzymes within the complex. Timing ensures division occurs after chromosome replication and segregation are adequately prepared.

Variability exists across bacteria. While FtsZ-based divisomes are common, some species lack FtsZ and use alternative division systems. Because divisomes are essential for viability, components are of interest as antibiotic targets, with research exploring inhibitors of FtsZ and associated division enzymes.