Role of staphylococcal EzrA as a molecular organizer of cell division

Abstract Envelope biogenesis in Staphylococcus aureus is concentrated at the septum and includes peptidoglycan synthesis, lipo- and wall-teichoic acid production, and the targeted secretion of YSIRK/GXXS signal peptide-bearing proteins. How S. aureus confines these processes to the dividing crosswall remains unclear. EzrA, a scaffolding protein structurally related to eukaryotic spectrins, has been implicated in linking cell division to envelope synthesis, yet its precise role is poorly understood. Here, we re-examine the function of EzrA for its contribution to envelope biogenesis and homeostasis. We observe that ezrA null mutants synthesize excess peptidoglycan that is incorporated in a dispersed pattern, no longer strictly confined to the septum. A similar loss of spatial restriction was observed for protein A, a surface protein whose YSIRK/GXXS signal peptide directs septal secretion and anchoring. In wild-type cells, newly synthesized peptidoglycan co-localized with nascent protein A anchoring sites at the septum, whereas this spatial coupling was disrupted in the absence of EzrA. In addition, loss of EzrA resulted in impaired nucleoid occlusion with septal guillotining of the chromosome. Together, these findings support a model in which EzrA acts as a molecular organizer of cell division, coordinating septal biosynthesis and envelope assembly while ensuring proper nucleoid occlusion.