Altouma, V. | Search bioRxiv

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↗

bioRxiv2025

Staphylococcus aureus exhibits spatiotemporal heterogeneity in Sae activity during kidney abscess development

Virulence factors are required for bacterial pathogens to establish infection, however, their expression can be energetically costly, and must be tightly controlled to avoid fitness costs. Expression can be controlled at specific stages during infection (temporal regulation) or expressed by small subsets of the bacterial population (spatial regulation). There has been a great deal of interest in developing virulence factor-targeting strategies to combat Staphylococcus aureus infection, but the spatiotemporal regulation of the virulence factor master regulatory systems (Agr, Sae) has not been explored during kidney abscess formation. This information is critical for the design of therapeutics targeting these pathways. Here, we utilized a fluorescent transcriptional reporter approach to visualize dynamics in Agr and Sae activity during abscess formation in the mouse kidney. We categorized kidney abscess formation into four stages, then defined spatiotemporal gene expression. Agr signalling appeared inactive in the kidney; consistent with this, agr mutant abscesses fully developed. In contrast, we observed heterogeneous (ON/OFF) activity of Sae at early stages where bacteria were found intracellularly within neutrophils. Sae activity increased as abscesses developed, and heterogeneity in spatial patterning was observed, but patterns varied between abscesses suggesting distinct microenvironments within individual abscesses. Consistent with a requirement for Sae activity during abscess development, the sae mutant did not develop abscesses past early stages. These results have implications for the genes regulated by Agr and Sae, and suggest a requirement for Sae activity during kidney abscess development. ImportanceInfections with Staphylococcus aureus pose a serious public health threat due to high levels of antibiotic resistance and limited efficacy of alternative therapeutics. There has been a great deal of interest in developing novel therapeutics that target virulence factors essential during infection. However, it remains largely unknown if these factors are required at specific stages of the infection, and whether all bacterial cells or a limited subset express them. Here we sought to examine virulence factor expression using fluorescent reporter strains that would indicate activity of two master regulators of virulence in S. aureus, Agr and Sae. While Agr appeared inactive during kidney abscess development, the Sae system exhibited heterogeneity, increased expression at later stages, and was required for abscess progression. These results provide critical information for the development of virulence factor-targeting strategies for kidney abscess treatment.

microbiology↗