FtsZ ring formation in fts mutants

The formation of FtsZ rings (Z rings) in various fts mutants was examined by immunoelectron microscopy and immunofluorescence. In two temperature-sensitive ftsZ mutants which form filaments with smooth morphology, the Z ring was unable to form. In ftsA, ftsI, and ftsQ mutants, which form filaments with an indented morphology, Z rings formed but their contraction was blocked. These results indicate that fully functional ftsA, ftsQ, and ftsI genes are not required for Z-ring formation and are unlikely to have a role in localization of the Z ring. The results also suggest that one function of the Z ring is to localize the activity of other fts gene products.