Pius, T. | bioRxiv Science

bioRxiv2026

Role of staphylococcal EzrA as a molecular organizer of cell division

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.

microbiology↗

bioRxiv2025

Inhibitory activities of monoclonal antibodies against Staphylococcus aureus Clumping factor A

Staphylococcus aureus infection is a frequent cause of sepsis in humans, a disease associated with high mortality and without specific intervention. Clumping factor A (ClfA) displayed on the bacterial surface plays a key role in promoting S. aureus replication during invasive disease. Decades of research have pointed to a wide array of ligands engaged by ClfA. The sum of these interactions supports the unique ability of this pathogen to survive and replicate in the blood stream. One such ligand is fibrin. ClfA acts as the key agglutinating factor of S. aureus by promoting the shielding of bacteria in fibrin cables and their physical escape from phagocytes. Here, we compare a series of monoclonal antibodies elicited against the ligand binding domain of ClfA following immunization of mice. We analyze these antibodies for their ability to neutralize ClfA interactions and to promote the uptake of staphylococci in whole blood. We find that while all the antibodies promoted opsonophagocytic uptake, only those that also inhibited ClfA interactions with ligands, reduced bacterial burdens in animals following blood stream challenge with S. aureus. IMPORTANCEAntibody-based approaches to fight bacterial pathogens have been modeled on toxin-producing or encapsulated pathogens for which correlates of protection can be reduced to measuring antibody neutralization or complement-fixing activities using tissue cultured cells. Such approaches have failed against Staphylococcus aureus raising uncertainty about the value of antibodies. Here, we use a series of mouse monoclonal antibodies directed against ClfA, a surface protein that allows S. aureus to thrive in the blood stream, to query how antibodies may be exploited against a pathogen endowed with a formidable array of virulence factors.

microbiology↗