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Deletion of the Alternative Sigma Factor ςB in Staphylococcus aureus Reveals Its Function as a Global Regulator of Virulence Genes
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A deletion of the sigB operon was constructed in three genetically distinct Staphylococcus aureus strains, and the phenotypes of the resulting mutants were analyzed. Compared to the corresponding wild-type strains, the ΔsigB mutants showed reduced pigmentation, accelerated sedimentation, and increased sensitivity to hydrogen peroxide during the stationary growth phase. A cytoplasmic protein missing in the ΔsigB mutants was identified as alkaline shock protein 23, and an extracellular protein excreted at higher levels in one of the ΔsigB mutants was identified as staphylococcal thermonuclease. Interestingly, most sigB deletion phenotypes were only seen in S. aureus COL and Newman and not in 8325, which was found to contain an 11-bp deletion in the regulator gene rsbU. Taken together, our results show that ςB is a global regulator which modulates the expression of several virulence factors in S. aureus and that laboratory strain 8325 is a ςB-defective mutant. 相似文献
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Role of ςB in Heat, Ethanol, Acid, and Oxidative Stress Resistance and during Carbon Starvation in Listeria monocytogenes
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To determine the contribution of sigma B (ςB) to survival of stationary-phase Listeria monocytogenes cells following exposure to environmental stresses, we compared the viability of strain 10403S with that of an isogenic nonpolar sigB null mutant strain after exposure to heat (50°C), ethanol (16.5%), or acid (pH 2.5). Strain viabilities were also determined under the same conditions in cultures that had been previously exposed to sublethal levels of the same stresses (45°C, 5% ethanol, or pH 4.5). The ΔsigB and wild-type strains had similar viabilities following exposure to ethanol and heat, but the ΔsigB strain was almost 10,000-fold more susceptible to lethal acid stress than its parent strain. However, a 1-h preexposure to pH 4.5 yielded a 1,000-fold improvement in viability for the ΔsigB strain. These results suggest the existence in L. monocytogenes of both a ςB-dependent mechanism and a pH-dependent mechanism for acid resistance in the stationary phase. ςB contributed to resistance to both oxidative stress and carbon starvation in L. monocytogenes. The ΔsigB strain was 100-fold more sensitive to 13.8 mM cumene hydroperoxide than the wild-type strain. Following glucose depletion, the ΔsigB strain lost viability more rapidly than the parent strain. ςB contributions to viability during carbon starvation and to acid resistance and oxidative stress resistance support the hypothesis that ςB plays a role in protecting L. monocytogenes against environmental adversities. 相似文献
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P. A. Fontán M. I. Voskuil M. Gomez D. Tan M. Pardini R. Manganelli L. Fattorini G. K. Schoolnik I. Smith 《Journal of bacteriology》2009,191(18):5628-5633
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Role of Listeria monocytogenes σB in Survival of Lethal Acidic Conditions and in the Acquired Acid Tolerance Response
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Adriana Ferreira David Sue Conor P. O'Byrne Kathryn J. Boor 《Applied microbiology》2003,69(5):2692-2698
The food-borne pathogen Listeria monocytogenes can acquire enhanced resistance to lethal acid conditions through multiple mechanisms. We investigated contributions of the stress-responsive alternative sigma factor, σB, which is encoded by sigB, to growth phase-dependent acid resistance (AR) and to the adaptive acid tolerance response in L. monocytogenes. At various points throughout growth, we compared the relative survival of L. monocytogenes wild-type and ΔsigB strains that had been exposed to either brain heart infusion (pH 2.5) or synthetic gastric fluid (pH 2.5) with and without prior acid adaptation. Under these conditions, survival of the ΔsigB strain was consistently lower than that of the wild-type strain throughout all phases of growth, ranging from 4 orders of magnitude less in mid-log phase to 2 orders of magnitude less in stationary phase. Survival of both ΔsigB and wild-type L. monocytogenes strains increased by 6 orders of magnitude upon entry into stationary phase, demonstrating that the L. monocytogenes growth phase-dependent AR mechanism is σB independent. σB-mediated contributions to acquired acid tolerance appear to be greatest in early logarithmic growth. Loss of a functional σB reduced the survival of L. monocytogenes at pH 2.5 to a greater extent in the presence of organic acid (100 mM acetic acid) than in the presence of inorganic acid alone (HCl), suggesting that L. monocytogenes protection against organic and inorganic acid may be mediated through different mechanisms. σB does not appear to contribute to pHi homeostasis through regulation of net proton movement across the cell membrane or by regulation of pHi buffering by the GAD system under the conditions examined in this study. In summary, a functional σB protein is necessary for full resistance of L. monocytogenes to lethal acid treatments. 相似文献
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The staphylococcal accessory regulator SarA and the alternative sigma factor σB have been previously identified as positive regulators, and IcaR as a negative regulator, of icaADBC expression. Here, we show that in Staphylococcus aureus SarA and σB are also required for icaR expression and that IcaR does not have a significant effect on its own expression. 相似文献
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Nielsen JS Olsen AS Bonde M Valentin-Hansen P Kallipolitis BH 《Journal of bacteriology》2008,190(18):6264-6270
In Listeria monocytogenes, the alternative sigma factor σB plays important roles in stress tolerance and virulence. Here, we present the identification of SbrA, a novel small noncoding RNA that is produced in a σB-dependent manner. This finding adds the σB regulon to the growing list of stress-induced regulatory circuits that include small noncoding RNAs. 相似文献
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Deletion of the sigB Gene in Bacillus cereus ATCC 14579 Leads to Hydrogen Peroxide Hyperresistance
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Willem van Schaik Marcel H. Zwietering Willem M. de Vos Tjakko Abee 《Applied microbiology》2005,71(10):6427-6430
The sigB gene of Bacillus cereus ATCC 14579 encodes the alternative sigma factor σB. Deletion of sigB in B. cereus leads to hyperresistance to hydrogen peroxide. The expression of katA, which encodes one of the catalases of B. cereus, is upregulated in the sigB deletion mutant, and this may contribute to the hydrogen peroxide-resistant phenotype. 相似文献
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beta-lactam antibiotics induce the SOS response and horizontal transfer of virulence factors in Staphylococcus aureus
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Maiques E Ubeda C Campoy S Salvador N Lasa I Novick RP Barbé J Penadés JR 《Journal of bacteriology》2006,188(7):2726-2729
Antibiotics that interfere with DNA replication and cell viability activate the SOS response. In Staphylococcus aureus, the antibiotic-induced SOS response promotes replication and high-frequency horizontal transfer of pathogenicity island-encoded virulence factors. Here we report that β-lactams induce a bona fide SOS response in S. aureus, characterized by the activation of the RecA and LexA proteins, the two master regulators of the SOS response. Moreover, we show that β-lactams are capable of triggering staphylococcal prophage induction in S. aureus lysogens. Consequently, and as previously described for SOS induction by commonly used fluoroquinolone antibiotics, β-lactam-mediated phage induction also resulted in replication and high-frequency transfer of the staphylococcal pathogenicity islands, showing that such antibiotics may have the unintended consequence of promoting the spread of bacterial virulence factors. 相似文献
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Characterization of the Starvation-Survival Response of Staphylococcus aureus 总被引:4,自引:0,他引:4
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The starvation-survival response of Staphylococcus aureus as a result of glucose, amino acid, phosphate, or multiple-nutrient limitation was investigated. Glucose and multiple-nutrient limitation resulted in the loss of viability of about 99 to 99.9% of the population within 2 days. The remaining surviving cells developed increased survival potential, remaining viable for months. Amino acid or phosphate limitation did not lead to the development of a stable starvation-survival state, and cells became nonculturable within 7 days. For multiple-nutrient limitation, the development of the starvation-survival state was cell density dependent. Starvation survival was associated with a decrease in cell size and increase in resistance to acid shock and oxidative stress. There was no evidence for the formation of a viable but nonculturable state during starvation as demonstrated by flow cytometry. Long-term survival of cells was dependent on cell wall and protein biosynthesis. Analysis of [35S]methionine incorporation and labelled proteins demonstrated that differential protein synthesis occurred deep into starvation. 相似文献
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Torsten Hartmann Grégory Baronian Nadine Nippe Meike Voss Bettina Schulthess Christiane Wolz Janina Eisenbeis Kerstin Schmidt-Hohagen Rosmarie Gaupp Cord Sunderk?tter Christoph Beisswenger Robert Bals Greg A. Somerville Mathias Herrmann Virginie Molle Markus Bischoff 《The Journal of biological chemistry》2014,289(43):29701-29711
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Strains of Staphylococcus aureus, an important human pathogen, display up to 20% variability in their genome sequence, and most sequence information is available for human clinical isolates that have not been subjected to genetic analysis of virulence attributes. S. aureus strain Newman, which was also isolated from a human infection, displays robust virulence properties in animal models of disease and has already been extensively analyzed for its molecular traits of staphylococcal pathogenesis. We report here the complete genome sequence of S. aureus Newman, which carries four integrated prophages, as well as two large pathogenicity islands. In agreement with the view that S. aureus Newman prophages contribute important properties to pathogenesis, fewer virulence factors are found outside of the prophages than for the highly virulent strain MW2. The absence of drug resistance genes reflects the general antibiotic-susceptible phenotype of S. aureus Newman. Phylogenetic analyses reveal clonal relationships between the staphylococcal strains Newman, COL, NCTC8325, and USA300 and a greater evolutionary distance to strains MRSA252, MW2, MSSA476, N315, Mu50, JH1, JH9, and RF122. However, polymorphism analysis of two large pathogenicity islands distributed among these strains shows that the two islands were acquired independently from the evolutionary pathway of the chromosomal backbones of staphylococcal genomes. Prophages and pathogenicity islands play central roles in S. aureus virulence and evolution. 相似文献
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