scholarly journals Petrobactin protects against oxidative stress and enhances sporulation efficiency inBacillus anthracisSterne

2018 ◽  
Author(s):  
Ada K. Hagan ◽  
Yael M. Plotnick ◽  
Ryan E. Dingle ◽  
Zachary I. Mendel ◽  
Stephen R. Cendrowski ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Bacillus Anthracis ◽  
Iron Acquisition ◽  
Sporulation Medium ◽  
Term Survival ◽  
Stress Protection ◽  
Sporulation Efficiency ◽  
Dormant Spore ◽  
Iron Iron

AbstractBacillus anthracisis a gram-positive bacillus that under conditions of environmental stress, such as low nutrients, can convert from a vegetative bacillus to a highly durable spore that enables long-term survival. The sporulation process is regulated by a sequential cascade of dedicated transcription factors but requires key nutrients to complete, one of which is iron. Iron acquisition by the iron-scavenging siderophore petrobactin is the only such system known to be required for vegetative growth ofB. anthracisin iron-depleted conditions,e.g., in the host. However, the extent to which petrobactin is involved in spore formation is unknown. This work shows that efficientin vitrosporulation ofB. anthracisrequires petrobactin, that the petrobactin biosynthesis operon (asbA-F) is induced prior to sporulation, and that petrobactin itself is associated with spores. Petrobactin is also required for both oxidative stress protection during late stage growth and wild-type levels of sporulation in sporulation medium. When considered with the petrobactin-dependent sporulation in bovine blood also described in this work, these effects onin vitrogrowth and sporulation suggest that petrobactin is required forB. anthracistransmission via the spore during natural infections in addition to its key functions during active anthrax infections.ImportanceBacillus anthraciscauses the disease anthrax, which is transmitted via its dormant, spore phase. However, converting from bacilli to spore is a complex, energetically costly process that requires many nutrients including iron.B. anthracisrequires the siderophore petrobactin to scavenge iron from host environments. We show that in the Sterne strain, petrobactin is required also for efficient sporulation, even when ample iron is available. The petrobactin biosynthesis operon is expressed during sporulation, and petrobactin is biosynthesized during growth in high iron sporulation medium but instead of being exported, the petrobactin remains intracellular to protect against oxidative stress and improve sporulation. It is also required for full growth and sporulation in blood (bovine), an essential step for anthrax transmission between mammalian hosts.

scholarly journals Petrobactin Protects against Oxidative Stress and Enhances Sporulation Efficiency inBacillus anthracisSterne

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Ada K. Hagan ◽  
Yael M. Plotnick ◽  
Ryan E. Dingle ◽  
Zachary I. Mendel ◽  
Stephen R. Cendrowski ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Bacillus Anthracis ◽  
Iron Acquisition ◽  
Sporulation Medium ◽  
Term Survival ◽  
Content Type ◽  
Stress Protection ◽  
Dormant Spore ◽  
Iron Iron

ABSTRACTBacillus anthracisis a Gram-positive bacillus that under conditions of environmental stress, such as low nutrients, can convert from a vegetative bacillus to a highly durable spore that enables long-term survival. The sporulation process is regulated by a sequential cascade of dedicated transcription factors but requires key nutrients to complete, one of which is iron. Iron acquisition by the iron-scavenging siderophore petrobactin is required for vegetative growth ofB. anthracisunder iron-depleted conditions and in the host. However, the extent to which petrobactin is involved in spore formation is unknown. This work shows that efficientin vitrosporulation ofB. anthracisrequires petrobactin, that the petrobactin biosynthesis operon (asbAto-F) is induced prior to sporulation, and that the siderophore itself associates with spores. Petrobactin is also required for oxidative stress protection during late-stage growth and for wild-type levels of sporulation in sporulation medium. Sporulation in bovine blood was found to be petrobactin dependent. Collectively, thein vitrocontributions of petrobactin to sporulation as well as growth imply that petrobactin may be required forB. anthracistransmission via the spore during natural infections, in addition to its key known functions during active anthrax infections.IMPORTANCEBacillus anthraciscauses the disease anthrax, which is transmitted via its dormant, spore phase. However, conversion from bacillus to spore is a complex, energetically costly process that requires many nutrients, including iron.B. anthracisrequires the siderophore petrobactin to scavenge iron from host environments. We show that, in the Sterne strain, petrobactin is required for efficient sporulation, even when ample iron is available. The petrobactin biosynthesis operon is expressed during sporulation, and petrobactin is biosynthesized during growth in high-iron sporulation medium, but instead of being exported, the petrobactin remains intracellular to protect against oxidative stress and improve sporulation. It is also required for full growth and sporulation in blood (bovine), an essential step for anthrax transmission between mammalian hosts.

An antioxidant role for catecholate siderophores in Salmonella

2013 ◽  
Vol 454 (3) ◽  
pp. 543-549 ◽  
Author(s):  
Maud E. S. Achard ◽  
Kaiwen W. Chen ◽  
Matthew J. Sweet ◽  
Rebecca E. Watts ◽  
Kate Schroder ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Ferric Iron ◽  
Iron Acquisition ◽  
Oxygen Species ◽  
Functional Studies ◽  
Host Pathogen Interaction ◽  
Host Pathogen ◽  
Very High ◽  
Full Protection

Iron acquisition is an important aspect of the host–pathogen interaction. In the case of Salmonella it is established that catecholate siderophores are important for full virulence. In view of their very high affinity for ferric iron, functional studies of siderophores have been almost exclusively focused on their role in acquisition of iron from the host. In the present study, we investigated whether the siderophores (enterobactin and salmochelin) produced by Salmonella enterica sv. Typhimurium could act as antioxidants and protect from the oxidative stress encountered after macrophage invasion. Our results show that the ability to produce siderophores enhanced the survival of Salmonella in the macrophage mainly at the early stages of infection, coincident with the oxidative burst. Using siderophore biosynthetic and siderophore receptor mutants we demonstrated that salmochelin and enterobactin protect S. Typhimurium against ROS (reactive oxygen species) in vitro and that siderophores must be intracellular to confer full protection. We also investigated whether other chemically distinct siderophores (yersiniabactin and aerobactin) or the monomeric catechol 2,3-dihydroxy-benzoate could provide protection against oxidative stress and found that only catecholate siderophores have this property. Collectively, the results of the present study identify additional functions for siderophores during host–pathogen interactions.

scholarly journals Evidence that Oxidative Stress InducesspxA2Transcription in Bacillus anthracis Sterne through a Mechanism Requiring SpxA1 and Positive Autoregulation

2016 ◽  
Vol 198 (21) ◽  
pp. 2902-2913 ◽  
Author(s):  
Skye Barendt ◽  
Cierra Birch ◽  
Lea Mbengi ◽  
Peter Zuber
Keyword(s):  
Oxidative Stress ◽  
Bacillus Anthracis ◽  
Transcription Initiation ◽  
Bacterial Species ◽  
Negative Control ◽  
Mobility Shift ◽  
Content Type ◽  
Oxidative Protein Damage

ABSTRACTBacillus anthracispossesses two paralogs of the transcriptional regulator, Spx. SpxA1 and SpxA2 interact with RNA polymerase (RNAP) to activate the transcription of genes implicated in the prevention and alleviation of oxidative protein damage. ThespxA2gene is highly upregulated in infected macrophages, but how this is achieved is unknown. Previous studies have shown that thespxA2gene was under negative control by the Rrf2 family repressor protein, SaiR, whose activity is sensitive to oxidative stress. These studies also suggested thatspxA2was under positive autoregulation. In the present study, we show byin vivoandin vitroanalyses thatspxA2is under direct autoregulation but is also dependent on the SpxA1 paralogous protein. The deletion of eitherspxA1orspxA2reduced the diamide-inducible expression of anspxA2-lacZconstruct.In vitrotranscription reactions using purifiedB. anthracisRNAP showed that SpxA1 and SpxA2 protein stimulates transcription from a DNA fragment containing thespxA2promoter. Ectopically positionedspxA2-lacZfusion requires both SpxA1 and SpxA2 for expression, but the requirement for SpxA1 is partially overcome whensaiRis deleted. Electrophoretic mobility shift assays showed that SpxA1 and SpxA2 enhance the affinity of RNAP forspxA2promoter DNA and that this activity is sensitive to reductant. We hypothesize that the previously observed upregulation ofspxA2in the oxidative environment of the macrophage is at least partly due to SpxA1-mediated SaiR repressor inactivation and the positive autoregulation ofspxA2transcription.IMPORTANCERegulators of transcription initiation are known to govern the expression of genes required for virulence in pathogenic bacterial species. Members of the Spx family of transcription factors function in control of genes required for virulence and viability in low-GC Gram-positive bacteria. InBacillus anthracis, thespxA2gene is highly induced in infected macrophages, which suggests an important role in the control of virulence gene expression during the anthrax disease state. We provide evidence that elevated concentrations of oxidized, active SpxA2 result from an autoregulatory positive-feedback loop drivingspxA2transcription.

Comparison of enzymically glucuronidated flavonoids with flavonoid aglycones in an in vitro cellular model of oxidative stress protection

2008 ◽  
Vol 44 (3-4) ◽  
pp. 73-80 ◽  
Author(s):  
David E. Stevenson ◽  
Janine M. Cooney ◽  
Dwayne J. Jensen ◽  
Reginald Wibisono ◽  
Aselle Adaim ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cellular Model ◽  
Flavonoid Aglycones ◽  
Stress Protection ◽  
Oxidative Stress Protection

scholarly journals Search for Bacillus anthracis Potential Vaccine Candidates by a Functional Genomic-Serologic Screen

2006 ◽  
Vol 74 (7) ◽  
pp. 3987-4001 ◽  
Author(s):  
Orit Gat ◽  
Haim Grosfeld ◽  
Naomi Ariel ◽  
Itzhak Inbar ◽  
Galia Zaide ◽  
...  
Keyword(s):  
Bacillus Anthracis ◽  
Vaccine Development ◽  
Iron Acquisition ◽  
Humoral Response ◽  
Open Reading Frames ◽  
Functional Annotations ◽  
Antigenic Properties ◽  
Experimental Findings ◽  
Related Proteins

ABSTRACTBacillus anthracisproteins that possess antigenic properties and are able to evoke an immune response were identified by a reductive genomic-serologic screen of a set of in silico-preselected open reading frames (ORFs). The screen included in vitro expression of the selected ORFs by coupled transcription and translation of linear PCR-generated DNA fragments, followed by immunoprecipitation with antisera fromB. anthracis-infected animals. Of the 197 selected ORFs, 161 were chromosomal and 36 were on plasmids pXO1 and pXO2, and 138 of the 197 ORFs had putative functional annotations (known ORFs) and 59 had no assigned functions (unknown ORFs). A total of 129 of the known ORFs (93%) could be expressed, whereas only 38 (64%) of the unknown ORFs were successfully expressed. All 167 expressed polypeptides were subjected to immunoprecipitation with the anti-B. anthracisantisera, which revealed 52 seroreactive immunogens, only 1 of which was encoded by an unknown ORF. The high percentage of seroreactive ORFs among the functionally annotated ORFs (37%; 51/129) attests to the predictive value of the bioinformatic strategy used for vaccine candidate selection. Furthermore, the experimental findings suggest that surface-anchored proteins and adhesins or transporters, such as cell wall hydrolases, proteins involved in iron acquisition, and amino acid and oligopeptide transporters, have great potential to be immunogenic. Most of the seroreactive ORFs that were tested as DNA vaccines indeed appeared to induce a humoral response in mice. We list more than 30 novelB. anthracisimmunoreactive virulence-related proteins which could be useful in diagnosis, pathogenesis studies, and future anthrax vaccine development.

scholarly journals Comparison of enzymically glucuronidated flavonoids with flavonoid aglycones in an in vitro cellular model of oxidative stress protection

2008 ◽  
Vol 44 (7) ◽  
pp. 303-303 ◽  
Author(s):  
David E. Stevenson ◽  
Janine M. Cooney ◽  
Dwayne J. Jensen ◽  
Reginald Wibisono ◽  
Aselle Adaim ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cellular Model ◽  
Flavonoid Aglycones ◽  
Stress Protection ◽  
Oxidative Stress Protection

DksA is a central regulatory switch for stress protection and virulence in Acinetobacter baumannii

2021 ◽  
Author(s):  
Ram Maharjan ◽  
Geraldine Sulivan ◽  
Felise Adams ◽  
Natasha Delgado ◽  
Lucie Semenec ◽  
...  
Keyword(s):  
Stress Response ◽  
Acinetobacter Baumannii ◽  
Galleria Mellonella ◽  
Resistance Mechanisms ◽  
Term Survival ◽  
In Vivo Models ◽  
Molecular Control ◽  
Stress Protection

Abstract Bacterial coordination of stress resistance mechanisms in harsh environments is key to long-term survival and evolutionary success. In many Gram-negative pathogens, both general- and specific-stress response are controlled by alternative sigma factors such as RpoS. The critically important pathogen Acinetobacter baumannii is notoriously recalcitrant to external stressors, yet it lacks RpoS, so the molecular control of its resilience remains unclear. Here, we used transposon insertion sequencing to characterize the molecular responses of Acinetobacter baumannii to two biologically-important metals stressors, zinc and copper, and discovered that the transcriptional regulator DksA acts as a major regulatory stress-protection switch. We mapped the highly pleiotropic nature of DksA using transcriptomics and phenomics and found that it controls ribosomal protein expression, metabolism of gluconeogenic substrates and survival in stresses that cause oxidative damage. A. baumannii strains lacking DksA were no longer virulent in both murine and Galleria mellonella in vivo models. In vitro, DksA mutants exhibited increased sensitivity to human serum and antibiotics yet promoted biofilm and capsule formation. Our study provides detailed insight into the unique role that DksA plays in stress protection and virulence for A. baumannii and lays the groundwork for understanding of RpoS-independent regulatory general stress response.

scholarly journals A Novel Sesquiterpene Lactone Xanthatin-13-(pyrrolidine-2-carboxylic acid) Isolated from Burdock Leaf Up-Regulates Cells’ Oxidative Stress Defense Pathway

Antioxidants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1617
Author(s):  
Yanis A. Idres ◽  
Didier Tousch ◽  
Guillaume Cazals ◽  
Aurélien Lebrun ◽  
Sarah Naceri ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Metabolic Syndrome ◽  
Carboxylic Acid ◽  
Sesquiterpene Lactone ◽  
In Vitro Test ◽  
Cellular Survival ◽  
Stress Protection ◽  
Docking Approach ◽  
Dimeric Form

The aim of our study was to identify novel molecules able to induce an adaptative response against oxidative stress during the first stages of metabolic syndrome. A cellular survival in vitro test against H2O2-based test was applied after pretreatment with various natural bitter Asteraceae extracts. This screening revealed potent protection from burdock leaf extract. Using chromatography and LC-MS—RMN, we then isolated and identified an original sesquiterpene lactone bioactive molecule: the Xanthatin-13-(pyrrolidine-2-carboxylic acid) (XPc). A real-time RT-qPCR experiment was carried out on three essential genes involved in oxidative stress protection: GPx, SOD, and G6PD. In presence of XPc, an over-expression of the G6PD gene was recorded, whereas no modification of the two others genes could be observed. A biochemical docking approach demonstrated that XPc had a high probability to directly interact with G6PD at different positions. One of the most probable docking sites corresponds precisely to the binding site of AG1, known to stabilize the G6PD dimeric form and enhance its activity. In conclusion, this novel sesquiterpene lactone XPc might be a promising prophylactic bioactive agent against oxidative stress and inflammation in chronic diseases such as metabolic syndrome or type 2 diabetes.

scholarly journals Reprioritization of biofilm metabolism is associated with nutrient adaptation and long-term survival of Haemophilus influenzae

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Alistair Harrison ◽  
Rachael L. Hardison ◽  
Rachel M. Wallace ◽  
James Fitch ◽  
Derek R. Heimlich ◽  
...  
Keyword(s):  
Haemophilus Influenzae ◽  
Biofilm Formation ◽  
Iron Acquisition ◽  
Heme Iron ◽  
Camp Phosphodiesterase ◽  
Term Survival ◽  
Nthi Strain ◽  
Stationary Phase Survival ◽  
Quantitative Analyses

Abstract Nontypeable Haemophilus influenzae (NTHI) is a human-restricted pathogen with an essential requirement for heme–iron acquisition. We previously demonstrated that microevolution of NTHI promotes stationary phase survival in response to transient heme–iron restriction. In this study, we examine the metabolic contributions to biofilm formation using this evolved NTHI strain, RM33. Quantitative analyses identified 29 proteins, 55 transcripts, and 31 metabolites that significantly changed within in vitro biofilms formed by RM33. The synthesis of all enzymes within the tryptophan and glycogen pathways was significantly increased in biofilms formed by RM33 compared with the parental strain. In addition, increases were observed in metabolite transport, adhesin production, and DNA metabolism. Furthermore, we observed pyruvate as a pivotal point in the metabolic pathways associated with changes in cAMP phosphodiesterase activity during biofilm formation. Taken together, changes in central metabolism combined with increased stores of nutrients may serve to counterbalance nutrient sequestration.

scholarly journals Effects of Endogenous d-Alanine Synthesis and Autoinhibition of Bacillus anthracis Germination on In Vitro and In Vivo Infections

2007 ◽  
Vol 75 (12) ◽  
pp. 5726-5734 ◽  
Author(s):  
Matthew T. McKevitt ◽  
Katie M. Bryant ◽  
Salika M. Shakir ◽  
Jason L. Larabee ◽  
Steven R. Blanke ◽  
...  
Keyword(s):  
Bacillus Anthracis ◽  
Lethal Dose ◽  
Threshold Effect ◽  
Experimental Conditions ◽  
In Vivo Experiments ◽  
Endogenous Production ◽  
Dormant Spore ◽  
Alanine Production

ABSTRACT Bacillus anthracis transitions from a dormant spore to a vegetative bacillus through a series of structural and biochemical changes collectively referred to as germination. The timing of germination is important during early steps in infection and may determine if B. anthracis survives or succumbs to responsive macrophages. In the current study experiments determined the contribution of endogenous d-alanine production to the efficiency and timing of B. anthracis spore germination under in vitro and in vivo conditions. Racemase-mediated production of endogenous d-alanine by B. anthracis altered the kinetics for initiation of germination over a range of spore densities and exhibited a threshold effect wherein small changes in spore number resulted in major changes in germination efficiency. This threshold effect correlated with d-alanine production, was prevented by an alanine racemase inhibitor, and required l-alanine. Interestingly, endogenous production of inhibitory levels of d-alanine was detected under experimental conditions that did not support germination and in a germination-deficient mutant of B. anthracis. Racemase-dependent production of d-alanine enhanced survival of B. anthracis during interaction with murine macrophages, suggesting a role for inhibition of germination during interaction with these cells. Finally, in vivo experiments revealed an approximately twofold decrease in the 50% lethal dose of B. anthracis spores administered in the presence of d-alanine, indicating that rates of germination may be directly influenced by the levels of this amino acid during early stages of disease.

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