Cell division inhibitors SulA and MinC/MinD block septum formation at different steps in the assembly of the Escherichia coli division machinery

SulA and MinCD are specific inhibitors of cell division in Escherichia coli . In this paper, size exclusion chromatography was used to study the effect of the SulA and MinCD division inhibitors on the oligomerization state of endogenous FtsZ in cytoplasmic extracts, and immunofluorescence microscopy was used to determine the effect of SulA and MinCD on the formation of FtsZ , FtsA and ZipA rings at potential division sites. SulA prevented the forma tion of high-molecular-weight FtsZ polymers by interfering with FtsZ dimeri zation and subsequent oligomerization. In contrast, the MinCD division inhi bitor did not prevent the oligomerization of FtsZ in the cell extracts or t he formation of FtsZ and ZipA ring structures in vivo. However, MinCD did p revent the formation of FtsA rings. Increased expression of ftsA suppressed MinCD-induced division inhibition, but had no effect on SulA-induced divis ion inhibition. These results indicate that MinCD blocks the assembly of th e septation machinery at a later step than SulA, at the stage at which FtsA is added to the FtsZ ring.