Prokaryotic cell division: flexible and diverse

• Many different routes lead to a productive Z-ring positioning.
• Assemblage of the mature division machinery takes approximately 20% of the cell cycle time in very diverse bacterial species.
• Direct interaction between proteins involved in cell elongation and in cell division is essential.
• Not all rod-shaped bacteria divide perpendicular to their length axes.

Gram-negative rod-shaped bacteria have different approaches to position the cell division initiating Z-ring at the correct moment in their cell division cycle. The subsequent maturation into a functional division machine occurs in vastly different species in two steps with appreciable time in between these. The function of this time delay is unclear, but may partly be explained by competition for Lipid-II between proteins involved in length growth that interact directly with the Z-ring early in the maturation phase and the proteins involved in septum synthesis. A second possible activity of the early Z-ring might be the monitoring of or the active involvement in DNA segregation through proteins such as ZapA and ZapB/MatP and their homologues.