Bacterial cytokinesis depends upon the tubulin-like GTPase FtsZ, which polymerizes into an annular structure at midcell (the Z-ring) that defines the division site. The Z-ring nucleates assembly of downstream machinery required for cell wall synthesis and membrane fission, but may also generate constrictive force. Recent high-resolution imaging of FtsZ in vivo has begun to illuminate the organization of filaments within the Z-ring. This in vivo work has been complemented by reconstitution of Z-rings in vitro to demonstrate the force-generating capacity of FtsZ and explore its mechanism of action. Despite these technical advances, whether FtsZ-mediated force generation is required for cytokinesis and how Z-ring structure and constriction are mechanistically linked to cell wall remodeling are open questions.
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