Biology subjects

Chabelskaya, S.

Publications and source records attributed to Chabelskaya, S..

4 recordsLinked to original sources

bioRxiv2026

Cross-regulatory sRNA networks shape adaptive stress responses in Staphylococcus aureus: RsaC and RsaOI regulate galactose metabolism and cell wall homeostasis

Staphylococcus aureus is a major human pathogen whose adaptability relies on network of regulators, including two-component systems, transcription factors and small regulatory RNAs. Yet most of these regulators are dispensable for growth, suggesting cooperation or redundancy between them. To explore this hypothesis, we performed a yeast one-hybrid screen of 43 TFs against the promoters of seven sRNAs, which identified 27 novel TF-sRNA promoter interactions. We then focused on three sRNAs. We showed that srn_9342 is repressed by VraR and MntR, which also control rsaOI and rsaC, respectively. We found that rsaC, like rsaOI, is induced by acidic pH and vancomycin exposure, whereas srn_9342 expression remained unchanged. We also demonstrated in vitro that Srn_9342 interacts with both RsaOI and RsaC. Its role toward these two sRNAs remains unknown, but this interaction raises the possibility that it modulates their availability or activity. RsaOI and RsaC both act on the tagatose pathway for galactose utilization, through different genes: lacD for RsaOI, as previously reported, and lacC for RsaC, newly identified here. We showed that both sRNAs are required for surface charge remodeling and for growth under subinhibitory vancomycin. They also modulate the virulence factors PSM and protein A. Both sRNAs reduce PSM production, whereas protein A is decreased by RsaOI, likely through Rot, and increased by RsaC through an unknown, probably indirect mechanism. Together, our results suggest that a single cell wall stress can engage several regulators that could cooperate on shared targets or pathways, which may explain why individual regulators are dispensable.

microbiology↗

bioRxiv2026

Ribo-seq reveals IsrR-mediated translational repression of SAOUHSC_02924 (gabT) during iron limitation in Staphylococcus aureus

Iron is essential for bacterial growth but can be toxic in excess. To maintain iron homeostasis, bacteria employ regulatory mechanisms, including small RNAs (sRNAs). In Staphylococcus aureus, we identified the sRNA IsrR as a critical mediator of the iron-sparing response, enabling bacterial fitness in iron-limited environments such as those encountered during host infection. Here, we use ribosome profiling (Ribo-seq) to define the translational regulatory network of IsrR under iron-limited conditions. Our analysis identifies multiple genes under IsrR control, including SAOUHSC_02924 (gabT), which encodes a putative 4-aminobutyrate aminotransferase. Given that IsrR downregulates iron-dependent TCA cycle enzymes, we propose that repression of gabT prevents the accumulation of TCA cycle precursors under iron depletion, thereby avoiding metabolic imbalances. These findings expand the role of IsrR in metabolic reprogramming and highlight its contribution to S. aureus survival in iron-restricted host niches.

microbiology↗

bioRxiv2025

Staphylococcus aureus derived extracellular vesicles trigger multiple inflammatory pathways in host cells and deliver their RNA cargo following their internalization and lysis within late endosomes

Staphylococcus aureus is a major opportunistic Gram-positive pathogen whose virulence can be partly mediated by extracellular vesicles (EVs). These nanosized particles carry a diverse cargo and can play key roles in host-pathogen interactions. Here, we investigated the production, composition, and host cell interactions of EVs secreted by the methicillin-resistant S. aureus strain N315, one of the most widely studied clinical isolates. To mimic infection, EVs produced from RPMI supplemented with 10% LB were purified by size exclusion chromatography, and characterized by nanoparticle tracking analysis and electron microscopy. N315 EVs contained a diverse molecular cargo, selectively enriched, and including proteins, lipoproteins, DNA, RNA, lipoteichoic acid, and peptidoglycan. Protection assays and confocal microscopy confirmed the intravesicular localization of RNAs and proteins. N315 EVs were recognized by multiple host pattern recognition receptors (PPRs) in human MG-63 cells, located at the cell surface (TLR1, TLR2, TLR4, TLR6), within endosomes (TLR3, TLR7, TLR4) and in the cytoplasm (NOD2). EV exposure promoted the selective upregulation of these PRRs, activated the NF-{kappa}B and JAK/STAT signaling pathways, and induced the expression of pro-inflammatory cytokines such as IL1{beta}, IL6, and CXCL8. N315 EVs were internalized via a dynamin-dependent endocytosis mechanism and trafficked to late endosomes, where RNA cargo release occurred. Importantly, inhibition of EVs uptake altered cytokine gene expression, confirming that internalization is required for immunomodulation. This work provides a better understanding of the mechanisms of interaction of S. aureus EVs with host cells and sheds light on the fate of EVs and their cargo once internalized by cells. IMPORTANCEAntibiotic resistance, coupled with the limited discovery of new antimicrobial agents, poses a growing threat to public health. Staphylococcus aureus is one of the six highly virulent and antibiotic-resistant bacterial species responsible for both severe hospital- and community-acquired infections. This pathogen demonstrates a remarkable ability to adapt to diverse hosts and environments and to produce a broad arsenal of virulence factors. Gaining deeper insight into its pathogenic mechanisms and host interactions may reveal novel therapeutic targets and alternative treatment strategies. Over the past decade, a key advancement has been the identification of extracellular vesicle production by S. aureus and its critical role as a new secretion system for virulence factors. This study shed light on the immunogenic effect of EVs and their role as a vehicle for the delivery of their contents into host cells. These adjuvant-like properties open new avenues for research and potential intervention.

microbiology↗

bioRxiv2024

sRNA-mediated crosstalk between cell wall stress and galactose metabolism in Staphylococcus aureus

Staphylococcus aureus is an opportunistic pathogen responsible for a wide range of diseases in humans. During infections, this bacterium is exposed to various stresses that target its cell wall, such as oxidative or acid environments as well as various cell wall-acting antimicrobials. S. aureus has effective regulatory systems for responding to environmental stresses enabling the expression of factors necessary for its survival. Bacterial small RNAs (sRNAs) play a crucial role in this adaptation process. In this study, we show that RsaOI, an S. aureus sRNA, accumulates under acid stress conditions. This response is mediated via the two-component system VraSR, which is associated with the cell wall damage response. As a component of the VraSR regulon, RsaOI contributes to the survival of S. aureus under acid stress and affects its susceptibility to glycopeptide antibiotics. Our findings reveal that RsaOI targets lacABCDFEG operon, which encodes components of tagatose pathway, a unique mechanism responsible for galactose metabolism in S. aureus. By antisense base pairing near the ribosome-binding site of lacD, RsaOI inhibits the expression of this gene, encoding tagatose-6-phosphate aldolase. This regulation disrupts the tagatose pathway, impairing galactose utilization in S. aureus. These findings highlight the role of RsaOI in the mediation between cell wall stress responses and specific metabolic pathway.

microbiology↗