Biology subjects

Missiakas, D. M.

Publications and source records attributed to Missiakas, D. M..

6 recordsLinked to original sources

bioRxiv2026

Orthogonal cell division organizes surface virulence factors to drive staphylococcal abscess community formation

During infection, Staphylococcus aureus forms dense multicellular structures, called staphylococcal abscess communities (SACs), that are encased in a capsule made of host fibrin to evade host immune defenses. S. aureus cells divide characteristically along successive orthogonal planes, but the contribution of this division geometry to infection is unclear. Here, we show that disrupting orthogonal cell division by deleting the cell division septum placement factor PcdA impairs SAC formation in vivo and in a three-dimensional in vitro model. Loss of PcdA leads to uneven surface distribution of adhesins containing the YSIRK signal sequence that directs their insertion into the division septum, thereby resulting in uneven interaction with fibrin fibers. Consequently, bacterial communities fail to establish a robust fibrin pseudocapsule and remain accessible to immune cells. We propose that orthogonal cell division coordinates cell cycle progression with extracellular matrix engagement, SAC architecture, and persistence within host tissues. HIGHLIGHTSO_LIOrthogonal cell division promotes staphylococcal abscess community formation C_LIO_LILoss of PcdA disrupts fibrin pseudocapsule assembly in 3D models C_LIO_LIDivision geometry ensures uniform surface deployment of adhesins C_LIO_LICell division plane selection links bacterial cell cycle control to virulence C_LI

microbiology↗

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↗

bioRxiv2023

Protein coopted from a phage restriction system dictates orthogonal cell division plane selection in Staphylococcus aureus

The spherical bacterium Staphylococcus aureus, a leading cause of nosocomial infections, undergoes binary fission by dividing in two alternating orthogonal planes, but the mechanism by which S. aureus correctly selects the next cell division plane is not known. To identify cell division placement factors, we performed a chemical genetic screen that revealed a gene which we termed pcdA. We show that PcdA is a member of the McrB family of AAA+ NTPases that has undergone structural changes and a concomitant functional shift from a restriction enzyme subunit to an early cell division protein. PcdA directly interacts with the tubulin-like central divisome component FtsZ and localizes to future cell division sites before membrane invagination initiates. This parallels the action of another McrB family protein, CTTNBP2, which stabilizes microtubules in animals. We show that PcdA also interacts with the structural protein DivIVA and propose that the DivIVA/PcdA complex recruits unpolymerized FtsZ to assemble along the proper cell division plane. Deletion of pcdA conferred abnormal, non-orthogonal division plane selection, increased sensitivity to cell wall-targeting antibiotics, and reduced virulence in a murine infection model. Targeting PcdA could therefore highlight a treatment strategy for combatting antibiotic-resistant strains of S. aureus.

microbiology↗

bioRxiv2022

Superiority of intranasal over systemic administration of bioengineered soluble ACE2 for survival and brain protection against SARS-CoV-2 infection

The present study was designed to investigate the effects of a soluble ACE2 protein termed ACE2 618-DDC-ABD, bioengineered to have long duration of action and high binding affinity to SARS-CoV-2, when administered either intranasally (IN) or intraperitoneally (IP) and before or after SARS-CoV-2 inoculation. K18hACE2 mice permissive for SARS-CoV-2 infection were inoculated with 2x104 PFU wildtype SARS-CoV-2. In one protocol, ACE2 618-DDC-ABD was given either IN or IP, pre- and post-viral inoculation. In a second protocol, ACE2 618-DDC-ABD was given either IN, IP or IN+IP but only post-viral inoculation. In addition, A549 and Vero E6 cells were used to test neutralization of SARS-CoV-2 variants by ACE2 618-DDC-ABD at different concentrations. Survival by day 5 was 0% in infected untreated mice, and 40% in mice from the ACE2 618-DDC-ABD IP-pre treated group. By contrast, in the IN-pre group survival was 90%, histopathology of brain and kidney was essentially normal and markedly improved in the lungs. When ACE2 618-DDC-ABD was administered only post viral inoculation, survival was 30% in the IN+IP group, 20% in the IN and 0% in the IP group. Brain SARS-CoV-2 titers were high in all groups except for the IN-pre group where titers were undetectable in all mice. In cells permissive for SARS-CoV-2 infection, ACE2 618-DDC-ABD neutralized wildtype SARS-CoV-2 at high concentrations, whereas much lower concentrations neutralized omicron BA. 1. We conclude that ACE2 618-DDC-ABD provides much better survival and organ protection when administered intranasally than when given systemically or after viral inoculation and that lowering brain titers is a critical determinant of survival and organ protection.

pathology↗

bioRxiv2021

A Protein A based Staphylococcus aureus vaccine with improved safety

Exposure to Staphylococcus aureus does not lead to immunity as evidenced by the persistent colonization of one third of the human population. S. aureus immune escape is mediated by factors that preempt complement activation, destroy phagocytes, and modify B and T cell responses. One such factor, Staphylococcal protein A (SpA) encompasses five Immunoglobulin binding domains (IgBDs) that associate with the Fc{gamma} domain to block phagocytosis. IgBDs also associate with the Fab domain of VH3-idiotypic IgM which activates B cells with the resulting secretion of antibodies that cannot bind determinants of S. aureus. SpA crosslinking of VH3-idiotypic IgG and IgE receptors of mast cells and basophils promotes histamine release and anaphylaxis. Previous work demonstrated the safety, immunogenicity, and protective efficacy of SpAKKAA, a variant partially defective for VH3-idiotypic Ig cross-linking, in murine models of S. aureus. Compared to mice (10%), humans produce significantly more VH3-idiotypic B cells (50%), prompting a search for safer SpA variants that may be suitably developed as clinical-grade vaccines for efficacy testing in humans. Here, we report the identification of such variants.

microbiology↗

bioRxiv2018

Septal Secretion of Protein A in Staphylococcus aureus Requires SecA and Lipoteichoic Acid Synthesis

Surface proteins of Staphylococcus aureus are secreted across septal membranes for assembly into the bacterial cross-wall. This localized secretion requires the YSIRK/GXXS motif signal peptide, however the mechanisms supporting precursor trafficking are not known. We show here that the signal peptide of staphylococcal protein A (SpA) is cleaved at the YSIRK/GXXS motif. A signal peptide mutant defective for cleavage can be crosslinked to SecA, SecDF and LtaS. SecA depletion blocks precursor targeting to septal membranes, whereas deletion of secDF diminishes SpA secretion into the cross-wall. Depletion of LtaS blocks lipoteichoic acid synthesis and promotes precursor trafficking to peripheral membranes. We propose a model whereby SecA directs SpA precursors to lipoteichoic acid-rich septal membranes for YSIRK/GXXS motif cleavage and secretion into the cross-wall.

microbiology↗