Biology subjects

Felton, E. A.

Publications and source records attributed to Felton, E. A..

5 recordsLinked to original sources

bioRxiv2026

SroA links SigS-dependent stress signaling to metabolic remodeling in Staphylococcus aureus

Staphylococcus aureus encounters diverse environmental conditions during colonization and infection, including fluctuations in nutrient availability, oxidative stress, and oxygen limitation. Adaptation to these environments requires regulatory systems that coordinate stress responses with metabolic remodeling. The extracytoplasmic function sigma factor SigS contributes to stress adaptation and virulence in S. aureus and directly activates expression of the sroAB operon, which encodes the small proteins SroA and SroB. While previous work demonstrated that SroA participates in feedback regulation of sigS expression, the broader physiological role of SroA has remained unclear. To define the regulatory functions of SroA, we performed RNA sequencing following inducible overexpression of sroA in S. aureus. Transcriptome analysis revealed extensive remodeling of gene expression, with approximately 200 transcripts significantly altered. Transcriptome analysis revealed coordinated repression of metabolic pathways (including nitrate respiration and nucleotide biosynthesis) alongside activation of stress-response and nutrient acquisition genes. Northern blot and quantitative RT-PCR analysis confirmed repression of narG and narJ transcripts following SroA overexpression. Consistent with these transcriptional changes, nitrate reduction assays demonstrated that SroA overexpression reduces nitrate respiration activity. In addition to repression of nitrate respiration genes, SroA overexpression broadly suppressed genes involved in de novo purine and pyrimidine biosynthesis. In contrast, transcripts associated with stress responses and nutrient acquisition, including the SOS-associated gene sosA and the phosphate transport gene pstS, were upregulated. Together, these findings identify SroA as a regulator that links stress-responsive signaling to metabolic remodeling in S. aureus, particularly through modulation of nitrate respiration pathways. ImportanceStaphylococcus aureus must rapidly adapt its metabolism to survive the diverse environments encountered during colonization and infection, including conditions where oxygen availability is limited. In this study, we identify a previously uncharacterized role for the small protein SroA in regulating metabolic adaptation in S. aureus. Transcriptome analysis revealed that SroA strongly represses genes involved in nitrate respiration, a pathway that enables bacteria to maintain energy production when oxygen is scarce. Consistent with these transcriptional changes, SroA overexpression reduced nitrate respiration activity. These findings reveal a regulatory link between stress-responsive signaling pathways and respiratory metabolism, expanding our understanding of how S. aureus adapts to oxygen-limited environments encountered during infection.

microbiology↗

bioRxiv2025

Genomic and Phenotypic Characterization of Mupirocin Resistant Staphylococcus aureus Clinical Isolates

BackgroundColonization with Staphylococcus aureus is a risk factor for subsequent infection. Decolonization with the topical antibiotic mupirocin is effective and reduces the risk of subsequent S. aureus infection for both methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) strains but may select for mupirocin-resistant isolates. MethodsWe characterized oxacillin and mupirocin susceptibility amongst 384 S. aureus strains isolated from clinical samples isolated 2017-2023 in Tampa, Florida, spanning strains collected before and after the onset of the COVID-19 pandemic. Whole genome sequencing of bacterial isolates was conducted in parallel and correlated with drug susceptibility profiles. ResultsMupirocin resistance (MupR) was nearly exclusively present in MRSA strains (103/106 97.1% of MupR; 103/299 34.4% of MRSA). Although our hospital protocol for decolonization shifted to povidone iodine in the Post-COVID period, the overall prevalence of MupR did not change in Pre-COVID and Post-COVID samples (28.9% vs 26%). Genotype correlated with antibiotic susceptibility with low level MupR (MupLR), linked to mutations in ileS and high level MupR (MupHR), linked to the presence of mupA. Genome analysis revealed that most MupR strains fell into three sequence types (ST) falling into two major clonal complexes (CC): CC8 ST8 (including Community-Associated MRSA strains USA300 and USA500), CC5 ST5 (associated with Healthcare-Associated MRSA such as USA100), and CC5 ST3390. ST3390 isolates had the highest prevalence of MupR (30/36 83%; MupHR 20/36 55.6%; MupLR 10/36 27.8%). ConclusionsMupirocin resistance was prevalent in our hospital MRSA strains. We also found evidence for emergence and persistence of ST3390 MRSA-MupR strains in Florida. Key pointsO_LIIn a survey of clinical isolates in Florida, 34.4% of MRSA strains were mupirocin resistant. C_LIO_LIMupirocin resistance correlated with mutations in ileS or carriage of mupA. C_LIO_LIWe found evidence for emergence of MRSA mupirocin-resistant strains that were sequence type ST3390. C_LI

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

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↗

bioRxiv2022

Staphylococcus aureus SigS induces expression of a regulatory protein pair that modulate its mRNA stability

SigS is the sole extracytoplasmic function sigma in S. aureus and is necessary for virulence, immune evasion, as well as surviving exposure to toxic chemicals and environmental stressors. Despite the contribution of SigS to a myriad of critical phenotypes, the downstream effectors of the SigS-dependent S. aureus pathogenesis, immune evasion, and stress response remain elusive. To address this knowledge gap, we analyzed the S. aureus transcriptome following transient over-expression of SigS. We identified a bi-cistronic transcript, up-regulated by 1000-fold, containing two mid-sized genes each containing single domains of unknown function (DUF). We renamed these genes sroA (SigS regulated orfA) and sroB (SigS regulated orfB). We demonstrated that the SigS regulation of the sroAB operon is direct using in vitro transcription analysis. Using northern blot analysis, we also demonstrated that SroA and SroB have opposing auto- regulatory functions on the transcriptional architecture of the sigS locus; with SroA stimulated SigS mRNA levels and SroB stimulating s750 (SigS antisense) levels. We hypothesized that these this opposing regulatory effects were due to a direct interaction. We demonstrated an interaction between SroA and SroB using an in-vivo surrogate genetics approach via Bacterial Two Hybrid. We demonstrated that the SroA effect on SigS is at the post-transcriptional level of mRNA stability, highlighting a mechanism likely used by S. aureus to tightly control SigS levels. Finally, we demonstrate that the sroAB locus promotes virulence in a female murine pneumonia model of infection.

microbiology↗