FTSZ IN BACILLUS-SUBTILIS IS REQUIRED FOR VEGETATIVE SEPTATION AND FOR ASYMMETRIC SEPTATION DURING SPORULATION

A Bacillus subtilis strain was constructed in which the cell division gene, ftsZ, was placed under control of the isopropyl-beta-D-thiogalactoside (IPTG)-inducible spac promoter. This strain was dependent upon the presence of IPTG for cell division and colony formation indicating that ftsZ is an essential cell division gene in this organism. In sporulation medium this strain increased in mass and reached stationary phase in the presence or absence of IPTG, but only sporulated in the presence of IPTG. The expression of the sporulation genes spoIIG, spoIIA, and spoIIE occurred normally in the absence of IPTG as monitored by spo-lacZ fusions. However, expression of lacZ fusions to genes normally induced later in the developmental pathway, and that required processed pro-sigma-E for expression was inhibited. Immunoblot analysis revealed that pro-sigma-E was not processed to its active form (sigma-E) under these experimental conditions. Electron microscopy revealed that these FtsZ-depleted cells did not initiate asymmetric septation, suggesting that FtsZ has a common role in the initiation of both the vegetative and sporulation septa.