FtsW is a dispensable cell division protein required for Z-ring stabilization during sporulation septation in Streptomyces coelicolor

The conserved rodA andftsW genes encode polytopic membrane proteins that are essential for bacterial cell elongation and division, respectively, and each gene is invariably linked with a cognate class B high-molecularweight penicillin-binding protein (HMW PBP) gene. Filamentous differentiating Streptomyces coelicolor possesses four such gene pairs. Whereas rodA, although not its cognate HMW PBP gene, is essential in these bacteria, mutation of SCO5302 or SC02607 (sfr) caused no gross changes to growth and septation. In contrast, disruption of eitherftsW or the cognateftsI gene blocked the formation of sporulation septa in aerial hyphae. The inability of spiral polymers of FtsZ to reorganize into rings in aerial hyphae of these mutants indicates an early pivotal role of an FtsW-FtsI complex in cell division. Concerted assembly of the complete divisome was unnecessary for Z-ring stabilization in aerial hyphae asftsQ mutants were found to be blocked at a later stage in cell division, during septum closure. Complete cross wall formation occurred in vegetative hyphae in all three fts mutants, indicating that the typical bacterial divisome functions specifically during nonessential sporulation septation, providing a unique opportunity to interrogate the function and dependencies of individual components of the divisome in vivo.