Biology subjects

Jobson, M.-E.

Publications and source records attributed to Jobson, M.-E..

5 recordsLinked to original sources

bioRxiv2026

SSR42 Enhances the Hemolytic Capacity of Staphylococcus aureus by Stabilizing the hla mRNA

Staphylococcus aureus utilizes a complex regulatory network to precisely control a vast array of virulence factors and facilitate infection. One such regulator, the long regulatory RNA SSR42, is emerging as a key modulator of virulence factor abundance and pathogenesis. Previous work has shown that a primary role for SSR42 is controlling hemolytic behavior through the positive regulation of -toxin (hla/Hla). Herein, we confirm that loss of SSR42 limits hemolytic capacity due to reduced Hla production. Others have suggested that this occurs through the SaeRS two-component system; however, using epistasis experiments, we reveal that SSR42 and SaeRS function independently to control Hla activity. Using a two-plasmid system optimized to detect regulatory RNA-mediated control in Gram-positive bacteria, we demonstrate that SSR42 directly enhances Hla production through the hla 5 untranslated region. Using interaction prediction and targeted mutagenesis, we identify a discrete site upstream of the hla ribosome-binding site that is required for SSR42 binding and hemolytic activity. Transcriptional arrest experiments further show that SSR42 stabilizes the hla mRNA, increasing its half-life and promoting downstream toxin production. Finally, electrophoretic mobility shift assays confirm a specific interaction between SSR42 and the hla 5 UTR. Collectively, these findings establish SSR42 as a major post-transcriptional regulator of S. aureus virulence and reveal a novel RNA-mediated mechanism that promotes -toxin production through stabilization of the hla transcript.

microbiology↗

bioRxiv2025

A single transcriptional regulator is crucial for the adaptation of Staphylococcus aureus to diverse niches

The adaptation of versatile multi-host pathogens to various hosts and various niches within hosts is often still poorly understood. The alternative Sigma factor B (SigB) is the master regulator of the general stress response of most gram-positive bacteria, which is a classic case of adaptive plasticity. In Staphylococcus aureus, SigB appears co-opted to function as a switch between intracellular and extracellular niches. During bovine mastitis, low SigB-activity confers an advantage in the milk-rich extracellular niche of the bovine udder. We show that narrowly adapted SigB-deficient strains evolved repeatedly from phenotypically plastic SigB-wildtype strains during persistent mastitis. This genetic assimilation appears driven by the cost of phenotypic plasticity: long time lags in adapting to milk and slow growth. Surprisingly, we observe that mutations causing SigB-deficiency allow even human isolates to grow in milk. While host adaptation often proceeds by mobile genetic elements exchanged between strains, we show how a master regulator in the core genome can drive niche adaptation.

microbiology↗

bioRxiv2025

Emergence of ST3390: A non-pigmented HA-MRSA clone with enhanced virulence

BackgroundOne of the most successful and widely-distributed hospital-associated lineages of MRSA is CC5. These strains are known from widespread antibiotic resistance, but less severe disease than CA-MRSA counterparts. Recently, CC5 descendant lineages have appeared globally with hypervirulent properties. MethodsHerein we use genomic analyses to study the epidemiology of a rare CC5 MRSA sequence type, ST3390, circulating within Tampa General Hospital (TGH). We employ genetic tools alongside in vitro and in vivo models of virulence to study the pathogenic capabilities of strains. ResultsTo date, there have only been 50 recorded instances of infection caused by ST3390 globally, with 36 of those occurring at TGH. Genomic analysis of strains identified numerous spa-types, with a t010 cluster found only at TGH. Exploration of AMR genes detected the presence of unique hybrid SCCmec types, with [~]90% of TGH strains possessing components of SCCmecIa, SCCmecIIa and/or SCCmecVIII. Phenotypically, all ST3390 strains lack the staphyloxanthin pigment, which is mediated by a conserved 6 aa in frame deletion within the staphyloxanthin biosynthesis protein CrtN. ST3390 strains display high levels of cytotoxicity towards human neutrophils compared to other CC5 lineages, with several isolates displaying hypervirulence in animal models of infection. ConclusionsThis is the first study to characterize the pathogenicity and genomic architecture of the rare MRSA lineage ST3390. Our work provides a deeper understanding of the clonal expansion of CC5, and the wider diversification of S. aureus isolates within patient populations.

microbiology↗

bioRxiv2024

Development of a New N-Terminomic Method to Study the Pathodegradome of the Staphylococcus aureus V8 Protease in Human Neutrophils

Staphylococcus aureus is a notorious human pathogen that relies on an array of virulence factors to engender infection and evade the host-immune system. Among these are the secreted proteases, which promote pathogenesis by degrading host proteins and modulating host-defenses. Human neutrophils play a pivotal role in these defenses, acting as the first responders against invading bacteria. While many S. aureus effectors of virulence have been shown to target leukocytes, there is limited knowledge on how the extracellular proteases modulate neutrophil fate. Typically, protease substrates have been identified in isolated settings using one at a time approaches; with neutrophil targets few and far between. Herein, we have developed a novel N-terminomic methodology termed TAGS-CR that can facilitate global substrate characterization in streamlined manner. We thus present the application of TAGS-CR to unravelling the human neutrophil pathodegradome of the S. aureus V8 protease. In so doing, we captured [~]350 V8 targets, revealing critical insight into how this virulence factor can modulate neutrophil functionality on various levels relevant to S. aureus disease progression. We recorded cleavage of proteins necessary for neutrophil adhesion and migration, a fundamental process necessary for pathogen clearance. Furthermore, we highlight V8 cleavage of proteins involved in important neutrophil defense tactics, such as degranulation and reactive oxygen species production. This protease may also facilitate bacterial dissemination via the intentional activation of neutrophil apoptosis. Collectively, this work deepens our understanding of host-pathogen interaction and begins to unravel how S. aureus proteases can induce immune dysregulation through the targeting of leukocytes. ImportanceDuring infection Staphylococcus aureus must engage and evade the host immune system in order to successfully cause disease. As neutrophils represent the frontline of defense against invading S. aureus cells, it becomes increasingly important to decode how this bacterium subverts their host-defense tactics. While the contributing role to neutrophil engagement for many S. aureus virulence factors have been elucidated, the effects of their proteases remain largely unclear. Here, we present a novel method for global protease substrate identification, TAGS-CR, and use it to identify S. aureus V8 protease targets in human neutrophils. These include factors that not only govern general neutrophil function but moreover, their defense mechanisms, such as migration, degranulation, oxidative defense, phagocytosis and apoptosis.

microbiology↗

bioRxiv2024

SSR42 is a Novel Regulator of Cytolytic Activity in Staphylococcus aureus

SSR42 is the longest noncoding RNA in the S. aureus cell and the second-most abundant transcript in the stationary phase transcriptome, second only to RNAIII. It is highly conserved across strains and exhibits pronounced stability in stationary phase, however the mechanism behind its regulatory role has yet to be fully elucidated. Herein, we used transcriptomic and proteomic approaches to probe the role of SSR42, revealing that it is a powerful, novel activator of the primary leukocidin LukAB. SSR42 is required for cytotoxicity towards, and escape from within, human neutrophils, and also mediates survival within human blood. We show that SSR42 wields this role via derepression by the peroxide repressor PerR in response to the presence of human neutrophils and governs lukAB induction in this niche. Importantly, this regulation is driven by direct RNA-RNA interaction, as we show binding of the 5 UTR of the lukAB transcript with the 3 end of SSR42, which ultimately modulates transcript stability as well as translational activity. Finally, we demonstrate that this behavior is absolutely required for full virulence of S. aureus in murine models of both pneumonia and sepsis. Collectively, we present SSR42 as a pleiotropic regulatory RNA that acts as a nexus between environmental sensing and the regulation of pathogenesis, responding to environmental stimuli and host immune factors to bolster cytotoxic behavior and facilitate infection in S. aureus. ImportanceS. aureus is a master pathogen due to its formidable collection of virulence factors. These are tightly controlled by a diverse group of regulators that titrate their abundance to adapt to unique infectious niches. The role of regulatory RNAs in stress adaptation and pathogenesis is becoming increasingly more relevant in S. aureus. In this study, we provide the most comprehensive global analysis to date of just such a factor, SSR42. Specifically, we uncover that SSR42 is required for mediating cytotoxicity - one of the pillars of infection - in response to phagocytosis by human neutrophils. We find that SSR42 is induced by components of the host immune system and facilitates downstream activation of cytotoxic factors via RNA-RNA interactions. This illustrates that SSR42 forms a pivotal link between sensing the external environment and mediating resistance to oxidative stress while promoting virulence, solidifying it as a major global regulator in S. aureus.

microbiology↗