CHARACTERIZATION OF THE ESSENTIAL CELL-DIVISION GENE FTSL (YLLD) OF BACILLUS-SUBTILIS AND ITS ROLE IN THE ASSEMBLY OF THE DIVISION APPARATUS

We have identified the Bacillus subtilis homologue of the essential ce ll division gene, ftsL, of Escherichia coli, Repression of ftsL in a s train engineered to carry a conditional promoter results in cell filam entation, with a near immediate arrest of cell division. The filaments show no sign of invagination, indicating that division is blocked at an early stage, ftsL is also shown to be required for septation during sporulation, and depletion of FtsL blocks the activation but not the synthesis of the prespore-specific sigma factor, sigma(F). Immunofluor escence microscopy shows that depletion of FtsL has little or no effec t on FtsZ ring formation, but the assembly of other division proteins, DivlB and DivlC, at the site of division is prevented. Repression of FtsL also results in a rapid loss of DivlC protein, indicating hat Div l2 stability is dependent on the presence of FtsL, in turn suggesting that FtsL is intrinsically unstable. The instability of one or more co mponents of the division apparatus may be important for the cyclic ass embly/disassembly of the division apparatus.