Biology subjects

Keim, K. C.

Publications and source records attributed to Keim, K. C..

3 recordsLinked to original sources

bioRxiv2024

Polymicrobial interactions between Staphylococcus aureus and Pseudomonas aeruginosa promote biofilm formation and persistence in chronic wound infections

Chronic, non-healing wounds are a leading cause of prolonged patient morbidity and mortality due to biofilm-associated, polymicrobial infections. Staphylococcus aureus and Pseudomonas aeruginosa are the most frequently co-isolated pathogens from chronic wound infections. Competitive interactions between these pathogens contribute to enhanced virulence, persistence, and antimicrobial tolerance. P. aeruginosa utilizes the extracellular proteases LasB, LasA, and AprA to degrade S. aureus surface structures, disrupt cellular physiology, and induce cell lysis, gaining a competitive advantage during co-infection. S. aureus evades P. aeruginosa by employing aggregation mechanisms to form biofilms. The cell wall protein SasG is implicated in S. aureus biofilm formation by facilitating intercellular aggregation upon cleavage by an extracellular protease. We have previously shown that proteolysis by a host protease can induce aggregation. In this study, we report that P. aeruginosa proteases LasA, LasB, and AprA cleave SasG to induce S. aureus aggregation. We demonstrate that SasG contributes to S. aureus biofilm formation in response to interactions with P. aeruginosa proteases by quantifying aggregation, SasG degradation, and proteolytic kinetics. Additionally, we assess the role of SasG in influencing S. aureus biofilm architecture during co-infection in vivo, chronic wound co-infections. This work provides further knowledge of some of the principal interactions that contribute to S. aureus persistence within chronic wounds co-infected with P. aeruginosa, and their impact on healing and infection outcomes.

microbiology↗

bioRxiv2023

Staphylococcus aureus skin colonization is mediated by SasG lectin variation

Staphylococcus aureus causes the majority of skin and soft tissue infections, but this pathogen only transiently colonizes healthy skin. However, this transient skin exposure enables S. aureus to transition to infection. Initial adhesion of S. aureus to skin corneocytes is mediated by surface protein G (SasG). Here, phylogenetic analyses reveal the presence of two major divergent SasG alleles in S. aureus, SasG-I and SasG-II. Structural analyses of SasG-II identified a unique non-aromatic arginine in the binding pocket of the lectin subdomain that mediates adhesion to corneocytes. Atomic force microscopy and corneocyte adhesion assays indicated SasG-II can bind to a broader variety of ligands than SasG-I. Glycosidase treatment resulted in different binding profiles between SasG-I and SasG-II on skin cells. Additionally, SasG-mediated adhesion was recapitulated using differentiated N/TERT keratinocytes. Our findings indicate that SasG-II has evolved to adhere to multiple ligands, conferring a distinct advantage to S. aureus during skin colonization.

microbiology↗

bioRxiv2022

Host-derived protease promotes aggregation of Staphylococcus aureus by cleaving the surface protein SasG

Staphylococcus aureus is one of the leading causes of hospital acquired infections, many of which begin following attachment and accumulation on indwelling medical devices or diseased tissue. These infections are often linked to establishment of biofilms, but another often overlooked key characteristic allowing S. aureus to establish persistent infection is formation of planktonic aggregates. Such aggregates are physiologically similar to biofilms and protect pathogen from innate immune clearance and increase its antibiotic tolerance. The cell wall-associated protein SasG has been implicated in biofilm formation via mechanisms of intercellular aggregation, but the mechanism in the context of disease is largely unknown. We have previously shown that expression of cell wall-anchored proteins involved in biofilm formation is controlled by the ArlRS-MgrA regulatory cascade. In this work, we demonstrate that the ArlRS two-component system controls aggregation, by repressing expression of sasG by activation of the global regulator MgrA. We also demonstrate that SasG must be proteolytically processed by a non-native protease to induce aggregation, and that strains expressing functional full-length sasG aggregate significantly upon proteolysis by a mucosal-derived host protease found in human saliva. We used fractionation and N-terminal sequencing to demonstrate that human trypsin within saliva cleaves within the A domain of SasG to expose the B domain and induce aggregation. Finally, we demonstrated that SasG is involved in virulence during mouse lung infection. Together, our data point to SasG, its processing by host proteases, and SasG-driven aggregation as important elements of S. aureus adaptation to host environment.

microbiology↗