2 POLYPEPTIDE PRODUCTS OF THE ESCHERICHIA-COLI CELL-DIVISION GENE FTSW AND A POSSIBLE ROLE FOR FTSW IN FTSZ FUNCTION

Two new mutations in the cell division gene ftsW have been isolated an d characterized. The ftsW263(Ts) mutation results in a block to divisi on at the initiation stage, similar to that previously observed with t he ftsW201(Ts) mutation. The ftsW1640(Ts) mutation, however, causes a block to division at a later stage. The ftsW201 and ftsW263 mutants we re shown to be phenotypically sensitive to the genetic background and growth conditions and are possibly relA dependent. Immunofluorescence microscopy showed that the FtsZ protein can localize to presumptive di vision sites in strains carrying ftsW(Ts) mutations at the nonpermissi ve temperature, suggesting that FtsW is unlikely to be specifically re quired for the localization of FtsZ to the division site. Examination of the localization of FtsZ in an ftsW rodA double mutant (lemon-shape d cells) revealed several classes of cells ranging from a common class where an FtsZ ring structure is absent to a class where FtsZ forms a complete ring at the midpoint of a lemon-shaped cell, suggesting a rol e for FtsW in the establishment of a stable FtsZ-based septal structur e. We further demonstrate that two FtsW peptides, FtsWL (large) and Ft sWS (small), can be identified and that the expression of ftsWS is suf ficient for complementation of fts(Ts) mutations.