Cell division inhibitors SulA and MinCD prevent formation of the FtsZ ring.

Immunoelectron microscopy was used to assess the effects of inhibitors of cell division on formation of the FtsZ ring in Escherichia coli. Induction of the cell division inhibitor SulA, a component of the SOS response, or the inhibitor MinCD, a component of the min system, blocked formation of the FtsZ ring and led to filamentation. Reversal of SulA inhibition by blocking protein synthesis in SulA-induced filaments led to a resumption of FtsZ ring formation and division. These results suggested that these inhibitors block cell division by preventing FtsZ localization into the ring structure. In addition, analysis of min mutants demonstrated that FtsZ ring formation was also associated with minicell formation, indicating that all septation events in E. coli involve the FtsZ ring.