Formation of the divisome protein complex in E. coli and in B. subtilis. A) Model for the assembly of proteins into the septal ring of E. coli. First, FtsZ forms a Z-ring. FtsA and ZipA are recruited next, independently from one another. Once both FtsA and ZipA have localized, the remaining proteins join the ring in the order indicated. B) Model for assembly of proteins into the septal ring during vegetative growth of B. subtilis. The assembly of late vegetative division proteins (FtsL, DivIB, DivIC and Pbp2B) is not linear and these components appear to assemble in a completely interdependent manner.