For E. coli cells, growth to a critical mass leads to initiation of chromosome replication. Initiation requires ATP-bound DnaA protein, together with replication proteins. Replication is followed by decatenation and monomerization of sister-chromosome molecules. Sister chromosomes are rapidly partitioned into opposite halves of the cell, perhaps by a kinesin-like protein (MukB). Cytokinesis starts with the formation of a ring of a GTP-binding protein (FtsZ), usually around the cell center. A specific enzyme (PBP3) and other proteins (FtsQ, FtsA, FtsL, FtsW) are responsible for the coordinate ingrowth of the peptidoglycan cell wall at this location. EnvA protein is required to split the resultant cross-wall to form new cell poles. The formation of the FtsZ ring is inhibited by activated MinC protein, but the MinE protein reverses this inhibition at potential division sites. A minimum cell length is probably required for partition and a minimum-size DNA-free zone for septum formation.