scholarly journals Stringent Response Governs the Virulence and Oxidative Stress Resistance of Francisella tularensis

2019 ◽  
Author(s):  
Zhuo Ma ◽  
Kayla King ◽  
Maha Alqahtani ◽  
Madeline Worden ◽  
Parthasarthy Muthuraman ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Francisella Tularensis ◽  
Stress Resistance ◽  
Stringent Response ◽  
Oxidative Stress Response ◽  
Stress Conditions ◽  
Gram Negative ◽  
And Oxidative Stress ◽  
Starvation Conditions

AbstractFrancisella tularensis is a Gram-negative bacterium responsible for causing tularemia in the northern hemisphere. F. tularensis has long been developed as a biological weapon due to its ability to cause severe illness upon inhalation of as few as ten organisms and based on its potential to be used as a bioterror agent is now classified as a Tier 1 Category A select agent by the CDC. The stringent response facilitates bacterial survival under nutritionally challenging starvation conditions. The hallmark of stringent response is the accumulation of the effector molecules ppGpp and (p)ppGpp known as stress alarmones. The relA and spoT gene products generate alarmones in several Gram-negative bacterial pathogens. RelA is a ribosome-associated ppGpp synthetase that gets activated under amino acid starvation conditions whereas, SpoT is a bifunctional enzyme with both ppGpp synthetase and ppGpp hydrolase activities. Francisella encodes a monofunctional RelA and a bifunctional SpoT enzyme. Previous studies have demonstrated that stringent response under nutritional stresses increases expression of virulence-associated genes encoded on Francisella Pathogenicity Island. This study investigated how stringent response governs the oxidative stress response of F. tularensis. We demonstrate that RelA/SpoT-mediated ppGpp production alters global gene transcriptional profile of F. tularensis in the presence of oxidative stress. The lack of stringent response in relA/spoT gene deletion mutants of F. tularensis makes bacteria more susceptible to oxidants, attenuates survival in macrophages, and virulence in mice. Mechanistically, we provide evidence that the stringent response in Francisella contributes to oxidative stress resistance by enhancing the production of antioxidant enzymes.ImportanceThe unique intracellular life cycle of Francisella in addition to nutritional stress also exposes the bacteria to oxidative stress conditions upon its brief residence in the phagosomes, and escape into the cytosol where replication takes place. However, the contribution of the stringent response in gene regulation and management of the oxidative stress response when Francisella is experiencing oxidative stress conditions is not known. Our results provide a link between the stringent and oxidative stress responses. This study further improves our understanding of the intracellular survival mechanisms of F. tularensis.

scholarly journals Inducible expression of (pp)pGpp synthetases in Staphylococcus aureus is associated with activation of stress response genes

2020 ◽  
Author(s):  
Petra Horvatek ◽  
Andrew Magdy Fekry Hanna ◽  
Fabio Lino Gratani ◽  
Daniela Keinhörster ◽  
Natalya Korn ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Staphylococcus Aureus ◽  
Stress Response ◽  
Stringent Response ◽  
Trna Synthetase ◽  
Oxidative Stress Response ◽  
Stress Conditions ◽  
Additional Stress ◽  
Iron Storage ◽  
Transcriptional Induction

AbstractThe stringent response is characterized by the synthesis of the messenger molecules pppGpp, ppGpp or pGpp (here collectively designated (pp)pGpp). The phenotypic consequences resulting from (pp)pGpp accumulation vary among species and can be mediated by different underlying mechanisms. Most genome-wide analyses have been performed under stress conditions, which often mask the immediate effects of (pp)pGpp-mediated regulatory circuits. In Staphylococcus aureus, (pp)pGpp can be synthesized via the RelA-SpoT-homolog (RSHSau) upon amino acid limitation or via one of the two small (pp)pGpp synthetases RelP or RelQ, upon cell wall stress. We used RNA-Seq to compare the global effects in response to transcriptional induction of the synthetase domain of RSH (RSH-Syn), RelP or RelQ without the need to apply additional stress conditions. Enzyme expression resulted in changes in the nucleotide pool similar to induction of the stringent response via the tRNA synthetase inhibitor mupirocin: a reduction in the GTP pool, an increase in the ATP pool and synthesis of pppGpp, ppGpp and pGpp. Induction of all three enzymes resulted in similar changes in the transcriptome. However, RelQ was less active than RSH-Syn and RelP, indicating strong restriction of its (pp)pGpp-synthesis activity in vivo. Genes involved in the SOS response, iron storage (e.g. ftnA, dps), oxidative stress response (e.g., katA, sodA) and the the psmα1-4 and psmß1-2 operons coding for cytotoxic, phenole soluble modulins (PSMs) were highly upregulated upon (pp)pGpp synthesis. Analyses of the ftnA, dps and psm genes in different regulatory mutants revealed that their (pp)pGpp-dependent regulation can occur independent of the regulators PerR, Fur, SarA or CodY. Moreover, psm expression is uncoupled from expression of the quorum sensing system Agr, the main known psm activator. The expression of central genes of the oxidative stress response protects the bacteria from anticipated ROS stress derived from PSMs or exogenous sources. Thus, we identified a new link between the stringent response and oxidative stress in S. aureus that is likely crucial for survival upon phagocytosis.SignificanceMost bacteria make use of the second messenger (pp)pGpp to reprogram bacterial metabolism under nutrient-limiting conditions. In the human pathogen Staphylococcus aureus, (pp)pGpp plays an important role in virulence, phagosomal escape and antibiotic tolerance. Here, we analyzed the immediate consequences of (pp)pGpp synthesis upon transcriptional induction of the (pp)pGpp-producing enzymes RSH, RelP or RelQ. (pp)pGpp synthesis provokes immediate changes in the nucleotide pool and severely impacts the expression of hundreds of genes. A main consequence of (pp)pGpp synthesis in S. aureus is the induction of ROS-inducing toxic phenol-soluble modulins (PSMs) and simultaneous expression of the detoxifying system to protect the producer. This mechanism is likely of special advantage for the pathogen after phagocytosis.

scholarly journals Inducible expression of (pp)pGpp synthetases in Staphylococcus aureus is associated with activation of stress response genes

PLoS Genetics ◽  
2020 ◽  
Vol 16 (12) ◽  
pp. e1009282
Author(s):  
Petra Horvatek ◽  
Andrea Salzer ◽  
Andrew Magdy Fekry Hanna ◽  
Fabio Lino Gratani ◽  
Daniela Keinhörster ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Staphylococcus Aureus ◽  
Stress Response ◽  
Stringent Response ◽  
Trna Synthetase ◽  
Oxidative Stress Response ◽  
Stress Conditions ◽  
Additional Stress ◽  
Iron Storage

The stringent response is characterized by the synthesis of the messenger molecules pppGpp, ppGpp or pGpp (here collectively designated (pp)pGpp). The phenotypic consequences resulting from (pp)pGpp accumulation vary among species and can be mediated by different underlying mechanisms. Most genome-wide analyses have been performed under stress conditions, which often mask the immediate effects of (pp)pGpp-mediated regulatory circuits. In Staphylococcus aureus, (pp)pGpp can be synthesized via the RelA-SpoT-homolog, RelSau upon amino acid limitation or via one of the two small (pp)pGpp synthetases RelP or RelQ upon cell wall stress. We used RNA-Seq to compare the global effects in response to induction of the synthetase of rel-Syn (coding for the enzymatic region of RelSau) or relQ without the need to apply additional stress conditions. Induction of rel-Syn resulted in changes in the nucleotide pool similar to induction of the stringent response via the tRNA synthetase inhibitor mupirocin: a reduction in the GTP pool, an increase in the ATP pool and synthesis of pppGpp, ppGpp and pGpp. Induction of all three enzymes resulted in similar changes in the transcriptome. However, RelQ was less active than Rel-Syn and RelP, indicating strong restriction of its (pp)pGpp-synthesis activity in vivo. (pp)pGpp induction resulted in the downregulation of many genes involved in protein and RNA/DNA metabolism. Many of the (pp)pGpp up-regulated genes are part of the GTP sensitive CodY regulon and thus likely regulated through lowering of the GTP pool. New CodY independent transcriptional changes were detected including genes involved in the SOS response, iron storage (e.g. ftnA, dps), oxidative stress response (e.g., perR katA, sodA) and the psmα1–4 and psmß1-2 operons coding for cytotoxic, phenol soluble modulins (PSMs). Analyses of the ftnA, dps and psm genes in different regulatory mutants revealed that their (pp)pGpp-dependent regulation can occur independent of the regulators PerR, Fur, SarA or CodY. Moreover, psm expression is uncoupled from expression of the quorum sensing system Agr, the main known psm activator. The expression of central genes of the oxidative stress response protects the bacteria from anticipated ROS stress derived from PSMs or exogenous sources. Thus, we identified a new link between the stringent response and oxidative stress in S. aureus that is likely crucial for survival upon phagocytosis.

Metformin inhibits the inflammatory and oxidative stress response induced by skin UVB-irradiation and provides 4-hydroxy-2-nonenal and nitrotyrosine formation and p53 protein activation

2020 ◽  
Vol 100 (2) ◽  
pp. 152-155
Author(s):  
Fernando Pinheiro Souza-Neto ◽  
Poliana Camila Marinello ◽  
Gabriela Pasqual Melo ◽  
Leandra Zambeli Naira Ramalho ◽  
Eliana M. Cela ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
P53 Protein ◽  
Oxidative Stress Response ◽  
Uvb Irradiation ◽  
Protein Activation ◽  
And Oxidative Stress

An AraC/XylS Family Transcriptional Regulator Modulates the Oxidative Stress Response of Francisella tularensis

2021 ◽  
Author(s):  
Dina Marghani ◽  
Zhuo Ma ◽  
Anthony J. Centone ◽  
Weihua Huang ◽  
Meenakshi Malik ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Francisella Tularensis ◽  
Human Disease ◽  
Transcriptional Regulator ◽  
Intracellular Survival ◽  
Gram Negative ◽  
Expression Of Genes ◽  
Transcription Regulators

Francisella tularensis is a Gram-negative bacterium that causes a fatal human disease known as tularemia. The Centers for Disease Control have classified F. tularensis as Category A Tier-1 Select Agent. The virulence mechanisms of Francisella are not entirely understood. Francisella possesses very few transcription regulators, and most of these regulate the expression of genes involved in intracellular survival and virulence. The F. tularensis genome sequence analysis reveals an AraC ( FTL_ 0689) transcriptional regulator homologous to the AraC/XylS family of transcriptional regulators. In Gram-negative bacteria, AraC activates genes required for L-arabinose utilization and catabolism. The role of the FTL_ 0689 regulator in F. tularensis is not known. In this study, we characterized the role of FTL_ 0689 in gene regulation of F. tularensis and investigated its contribution to intracellular survival and virulence. The results demonstrate that FTL_0689 in Francisella is not required for L-arabinose utilization. Instead, FTL_ 0689 specifically regulates the expression of the oxidative and global stress response, virulence, metabolism, and other key pathways genes required by Francisella when exposed to oxidative stress. The FTL_0689 mutant is attenuated for intramacrophage growth and virulence in mice. Based on the deletion mutant phenotype, FTL_0689 was termed osrR ( o xidative s tress r esponse r egulator). Altogether, this study elucidates the role of the osrR transcriptional regulator in tularemia pathogenesis. IMPORTANCE: The virulence mechanisms of category A select agent Francisella tularensis , the causative agent of a fatal human disease known as tularemia, remain largely undefined. The present study investigated the role of a transcriptional regulator and its overall contribution to the oxidative stress resistance of F. tularensis . The results provide an insight into a novel gene regulatory mechanism, especially when Francisella is exposed to oxidative stress conditions. Understanding such Francisella - specific regulatory mechanisms will identify potential targets for developing effective therapies and vaccines to prevent tularemia.

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