Intersection of phosphate transport, oxidative stress and TOR signalling inCandida albicansvirulence

AbstractPhosphate is an essential macronutrient required for cell growth and division. Pho84 is the major high-affinity cell-surface phosphate importer ofSaccharomyces cerevisiaeand a crucial element in the phosphate homeostatic system of this model yeast. We found that loss ofCandida albicansPho84 attenuated virulence inDrosophilaand murine oropharyngeal and disseminated models of invasive infection, and conferred hypersensitivity to neutrophil killing. Susceptibility of cells lacking Pho84 to neutrophil attack depended on reactive oxygen species (ROS):pho84-/-cells were no more susceptible than wild typeC. albicansto neutrophils from a patient with chronic granulomatous disease, or to those whose oxidative burst was pharmacologically inhibited or neutralized.pho84-/-mutants hyperactivated oxidative stress signalling. They accumulated intracellular ROS in the absence of extrinsic oxidative stress, in high as well as low ambient phosphate conditions. ROS accumulation correlated with diminished levels of the unique superoxide dismutase Sod3 inpho84-/-cells, whileSOD3overexpression from a conditional promoter substantially restored these cells’ oxidative stress resistance in vitro. Repression ofSOD3expression sharply increased their oxidative stress hypersensitivity. Neither of these oxidative stress management effects of manipulatingSOD3transcription was observed inPHO84wild type cells. Sod3 levels were not the only factor driving oxidative stress effects onpho84-/-cells, though, because overexpressingSOD3did not ameliorate these cells’ hypersensitivity to neutrophil killing ex vivo, indicating Pho84 has further roles in oxidative stress resistance and virulence. Measurement of cellular metal concentrations demonstrated that diminished Sod3 expression was not due to decreased import of its metal cofactor manganese, as predicted from the function ofS. cerevisiaePho84 as a low-affinity manganese transporter. Instead of a role of Pho84 in metal transport, we found its role in TORC1 activation to impact oxidative stress management: overexpression of the TORC1-activating GTPase Gtr1 relieved the Sod3 deficit and ROS excess inpho84-/-null mutant cells, though it did not suppress their hypersensitivity to neutrophil killing or hyphal growth defect. Pharmacologic inhibition of Pho84 by small molecules including the FDA-approved drug foscarnet also induced ROS accumulation. Inhibiting Pho84 could hence support host defenses by sensitizingC. albicansto oxidative stress.

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Streblus asper Lour. exerts MAPK and SKN-1 mediated anti-aging, anti-photoaging activities and imparts neuroprotection by ameliorating Aβ in Caenorhabditis elegans

Nutrition and Healthy Aging ◽

10.3233/nha-210121 ◽

2021 ◽

pp. 1-17

Author(s):

Mani Iyer Prasanth ◽

James Michael Brimson ◽

Dicson Sheeja Malar ◽

Anchalee Prasansuklab ◽

Tewin Tencomnao

Keyword(s):

Oxidative Stress ◽

Caenorhabditis Elegans ◽

Stress Resistance ◽

Vital Role ◽

Transgenic Strain ◽

Wild Type ◽

Neuroprotective Effects ◽

C Elegans ◽

Streblus Asper

BACKGROUND: Streblus asper Lour., has been reported to have anti-aging and neuroprotective efficacies in vitro. OBJECTIVE: To analyze the anti-aging, anti-photoaging and neuroprotective efficacies of S. asper in Caenorhabditis elegans. METHODS: C. elegans (wild type and gene specific mutants) were treated with S. asper extract and analyzed for lifespan and other health benefits through physiological assays, fluorescence microscopy, qPCR and Western blot. RESULTS: The plant extract was found to increase the lifespan, reduce the accumulation of lipofuscin and modulate the expression of candidate genes. It could extend the lifespan of both daf-16 and daf-2 mutants whereas the pmk-1 mutant showed no effect. The activation of skn-1 was observed in skn-1::GFP transgenic strain and in qPCR expression. Further, the extract can extend the lifespan of UV-A exposed nematodes along with reducing ROS levels. Additionally, the extract also extends lifespan and reduces paralysis in Aβ transgenic strain, apart from reducing Aβ expression. CONCLUSIONS: S. asper was able to extend the lifespan and healthspan of C. elegans which was independent of DAF-16 pathway but dependent on SKN-1 and MAPK which could play a vital role in eliciting the anti-aging, anti-photoaging and neuroprotective effects, as the extract could impart oxidative stress resistance and neuroprotection.

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Proline Metabolism IncreaseskatGExpression and Oxidative Stress Resistance in Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.02282-14 ◽

2014 ◽

Vol 197 (3) ◽

pp. 431-440 ◽

Cited By ~ 41

Author(s):

Lu Zhang ◽

James R. Alfano ◽

Donald F. Becker

Keyword(s):

Oxidative Stress ◽

Escherichia Coli ◽

Hydrogen Peroxide ◽

Mutant Strain ◽

Stress Resistance ◽

Proline Metabolism ◽

Wild Type ◽

Content Type ◽

Oxidative Stress Resistance ◽

Proline Utilization

The oxidation ofl-proline to glutamate in Gram-negative bacteria is catalyzed by the proline utilization A (PutA) flavoenzyme, which contains proline dehydrogenase (PRODH) and Δ1-pyrroline-5-carboxylate (P5C) dehydrogenase domains in a single polypeptide. Previous studies have suggested that aside from providing energy, proline metabolism influences oxidative stress resistance in different organisms. To explore this potential role and the mechanism, we characterized the oxidative stress resistance of wild-type andputAmutant strains ofEscherichia coli. Initial stress assays revealed that theputAmutant strain was significantly more sensitive to oxidative stress than the parental wild-type strain. Expression of PutA in theputAmutant strain restored oxidative stress resistance, confirming that depletion of PutA was responsible for the oxidative stress phenotype. Treatment of wild-type cells with proline significantly increased hydroperoxidase I (encoded bykatG) expression and activity. Furthermore, the ΔkatGstrain failed to respond to proline, indicating a critical role for hydroperoxidase I in the mechanism of proline protection. The global regulator OxyR activates the expression ofkatGalong with several other genes involved in oxidative stress defense. In addition tokatG, proline increased the expression ofgrxA(glutaredoxin 1) andtrxC(thioredoxin 2) of the OxyR regulon, implicating OxyR in proline protection. Proline oxidative metabolism was shown to generate hydrogen peroxide, indicating that proline increases oxidative stress tolerance inE. colivia a preadaptive effect involving endogenous hydrogen peroxide production and enhanced catalase-peroxidase activity.

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Role of ςB in Heat, Ethanol, Acid, and Oxidative Stress Resistance and during Carbon Starvation inListeria monocytogenes

Applied and Environmental Microbiology ◽

10.1128/aem.67.10.4454-4457.2001 ◽

2001 ◽

Vol 67 (10) ◽

pp. 4454-4457 ◽

Cited By ~ 170

Author(s):

Adriana Ferreira ◽

Conor P. O'Byrne ◽

Kathryn J. Boor

Keyword(s):

Oxidative Stress ◽

Stationary Phase ◽

Stress Resistance ◽

Parent Strain ◽

Acid Resistance ◽

Carbon Starvation ◽

Wild Type ◽

Oxidative Stress Resistance ◽

And Oxidative Stress ◽

Dependent Mechanism

ABSTRACT To determine the contribution of sigma B (ςB) to survival of stationary-phase Listeria monocytogenescells following exposure to environmental stresses, we compared the viability of strain 10403S with that of an isogenic nonpolarsigB 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 inL. 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.

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In Staphylococcus aureus, Fur Is an Interactive Regulator with PerR, Contributes to Virulence, and Is Necessary for Oxidative Stress Resistance through Positive Regulation of Catalase and Iron Homeostasis

Journal of Bacteriology ◽

10.1128/jb.183.2.468-475.2001 ◽

2001 ◽

Vol 183 (2) ◽

pp. 468-475 ◽

Cited By ~ 187

Author(s):

Malcolm J. Horsburgh ◽

Eileen Ingham ◽

Simon J. Foster

Keyword(s):

Oxidative Stress ◽

Staphylococcus Aureus ◽

Stress Resistance ◽

Metal Ion ◽

Iron Homeostasis ◽

Antioxidant Properties ◽

Tetracycline Resistance ◽

Growth Defect ◽

Oxidative Stress Resistance

ABSTRACT The Staphylococcus aureus genome encodes three ferric uptake repressor (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of Fur in S. aureus, we inactivated thefur gene by allelic replacement using a tetracycline resistance cassette, creating strain MJH010 (fur). The mutant had a growth defect in rich medium, and this defect was exacerbated in metal-depleted CL medium. This growth defect was partially suppressed by manganous ion, a metal ion with known antioxidant properties. This suggests that the fur mutation leads to an oxidative stress condition. Indeed, MJH010 (fur) has reduced levels of catalase activity resulting from decreased katA transcription. Using akatA-lacZ fusion we have determined that Fur functions, either directly or indirectly, as an iron-dependent positive regulator of katA expression. Transcription of katA is coregulated by Fur and PerR, since in MJH010 (fur) transcription was still repressed by manganese while transcription in MJH201 (fur perR) was unresponsive to the presence of iron or manganese. Siderophore biosynthesis was repressed by iron in 8325-4 (wild-type) but in MJH010 (fur) was constitutive. A number of putative Fur-regulated genes were identified in the incomplete genome databases using known S. aureus Fur box sequences. Of those tested, the sstABCD andsirABC operons and the fhuD2 andorf4 genes were found to have Fur-regulated expression. MJH010 (fur) was attenuated (P < 0.04) in a murine skin abscess model of infection, as was double-mutant MJH201 (fur perR) (P < 0.03). This demonstrates the importance in vivo of iron homeostasis and oxidative stress resistance regulation in S. aureus.

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Contribution of the Helicobacter pylori Thiol Peroxidase Bacterioferritin Comigratory Protein to Oxidative Stress Resistance and Host Colonization

Infection and Immunity ◽

10.1128/iai.73.1.378-384.2005 ◽

2005 ◽

Vol 73 (1) ◽

pp. 378-384 ◽

Cited By ~ 68

Author(s):

Ge Wang ◽

Adriana A. Olczak ◽

James P. Walton ◽

Robert J. Maier

Keyword(s):

Oxidative Stress ◽

Mutant Strain ◽

Stress Resistance ◽

Type Strain ◽

Wild Type Strain ◽

Wild Type ◽

Oxidative Stress Resistance ◽

Organic Hydroperoxides ◽

H Pylori ◽

Thiol Peroxidase

ABSTRACT Peroxiredoxins, the enzymes that catalyze the reduction of hydrogen peroxide and organic hydroperoxides, are ubiquitous proteins that protect organisms from damage by reactive oxygen species. Helicobacter pylori contains three members of the peroxiredoxin family: AhpC (alkyl hydroperoxide reductase), Tpx (thiol-specific peroxidase), and bacterioferritin comigratory protein (BCP). In this study, we characterized H. pylori bcp mutant strains and wild-type BCP. Compared to the parent strain and the ahpC mutant strain, the bcp mutant showed moderate sensitivity to the superoxide-generating agent paraquat and to organic hydroperoxides. Upon exposure of 108 cells to air for 10 h, 106 wild-type cells survived but none of the 108 bcp mutant cells were recovered. Introduction of an intact bcp gene at an unrelated locus in the bcp strain restored the wild-type-like oxidative stress resistance phenotype. Purified BCP was shown to be a thiol peroxidase that depends on the reducing activity of thioredoxin and thioredoxin reductase. Among a series of peroxides tested, linoleic acid hydroperoxide was the preferred substrate of BCP. By examining the profiles of protein expression within H. pylori cells, we confirmed that AhpC is much more abundant than BCP. The overlapping functions and activities of BCP and AhpC probably explain why the bcp mutant displayed a relatively weak oxidative stress resistance phenotype. The bcp mutant strain could colonize mouse stomachs, although colonization by the wild-type strain was slightly better than that by the mutant strain at 1 week after host inoculation. However, at 3 weeks after inoculation, the colonization ability of the wild type was significantly greater than that of the bcp mutant; for example, H. pylori was recovered from 10 of 11 mouse stomachs inoculated with the wild-type strain but from only 4 of 12 mice that were inoculated with the bcp mutant strain. This indicates that H. pylori BCP plays a significant role in efficient host colonization.

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Integrative Conjugative Element ICE-βox Confers Oxidative Stress Resistance to Legionella pneumophila In Vitro and in Macrophages

mBio ◽

10.1128/mbio.01091-14 ◽

2014 ◽

Vol 5 (3) ◽

Cited By ~ 16

Author(s):

Kaitlin J. Flynn ◽

Michele S. Swanson

Keyword(s):

Oxidative Stress ◽

Legionella Pneumophila ◽

Stress Resistance ◽

Phenotype Microarray ◽

Bacterial Survival ◽

Content Type ◽

Oxidative Stress Resistance ◽

Phagocyte Oxidase ◽

Integrative Conjugative Elements

ABSTRACTIntegrative conjugative elements (ICEs) are mobile blocks of DNA that can contribute to bacterial evolution by self-directed transmission of advantageous traits. Here, we analyze the activity of a putative 65-kb ICE harbored byLegionella pneumophilausing molecular genetics, conjugation assays, a phenotype microarray screen, and macrophage infections. The element transferred to a naiveL. pneumophilastrain, integrated site-specifically, and conferred increased resistance to oxacillin, penicillin, hydrogen peroxide, and bleach. Furthermore, the element increased survival ofL. pneumophilawithin restrictive mouse macrophages. In particular, this ICE protectsL. pneumophilafrom phagocyte oxidase activity, since mutation of the macrophage NADPH oxidase eliminated the fitness difference between strains that carried and those that lacked the mobile element. Renamed ICE-βox (forβ-lactam antibiotics andoxidative stress), this transposable element is predicted to contribute to the emergence ofL. pneumophilastrains that are more fit in natural and engineered water systems and in macrophages.IMPORTANCEBacteria evolve rapidly by acquiring new traits via horizontal gene transfer. Integrative conjugative elements (ICEs) are mobile blocks of DNA that encode the machinery necessary to spread among bacterial populations. ICEs transfer antibiotic resistance and other bacterial survival factors as cargo genes carried within the element. Here, we show thatLegionella pneumophila, the causative agent of Legionnaires’ disease, carries ICE-βox, which enhances the resistance of this opportunistic pathogen to bleach and β-lactam antibiotics. Moreover,L. pneumophilastrains encoding ICE-βox are more resistant to macrophages that carry phagocyte oxidase. Accordingly, ICE-βox is predicted to increase the fitness ofL. pneumophilain natural and engineered waters and in humans. To our knowledge, this is the first description of an ICE that confers oxidative stress resistance to a nosocomial pathogen.

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Oxidative-Stress Resistance Mutants of Helicobacter pylori

Journal of Bacteriology ◽

10.1128/jb.184.12.3186-3193.2002 ◽

2002 ◽

Vol 184 (12) ◽

pp. 3186-3193 ◽

Cited By ~ 79

Author(s):

Adriana A. Olczak ◽

Jonathan W. Olson ◽

Robert J. Maier

Keyword(s):

Oxidative Stress ◽

Stress Resistance ◽

Double Mutant ◽

Mutation Frequency ◽

Spontaneous Mutation ◽

Type I ◽

Wild Type ◽

Oxidative Stress Resistance ◽

Spontaneous Mutation Frequency ◽

Resistance Mutants

ABSTRACT Within a large family of peroxidases, one member that catalyzes the reduction of organic peroxides to alcohols is known as alkyl hydroperoxide reductase, or AhpC. Gene disruption mutations in the gene encoding AhpC of Helicobacter pylori (ahpC) were generated by screening transformants under low-oxygen conditions. Two classes of mutants were obtained. Both types lack AhpC protein, but the major class (type I) isolated was found to synthesize increased levels (five times more than the wild type) of another proposed antioxidant protein, an iron-binding, neutrophil-activating protein (NapA). The other class of mutants, the minor class (type II), produced wild-type levels of NapA. The two types of AhpC mutants differed in their frequencies of spontaneous mutation to rifampin resistance and in their sensitivities to oxidative-stress chemicals, with the type I mutants exhibiting less sensitivity to organic hydroperoxides as well as having a lower mutation frequency. The napA promoter regions of the two types of AhpC mutants were identical, and primer extension analysis revealed their transcription start site to be the same as for the wild type. Gene disruption mutations were obtained in napA alone, and a double mutant strain (ahpC napA) was also created. All four of the oxidative-stress resistance mutants could be distinguished from the wild type in oxygen sensitivity or in some other oxidative-stress resistance phenotype (i.e., in sensitivity to stress-related chemicals and spontaneous mutation frequency). For example, growth of the NapA mutant was more sensitive to oxygen than that of the wild-type strain and both of the AhpC-type mutants were highly sensitive to paraquat and to cumene hydroperoxide. Of the four types of mutants, the double mutant was the most sensitive to growth inhibition by oxygen and by organic peroxides and it had the highest spontaneous mutation frequency. Notably, two-dimensional gel electrophoresis combined with protein sequence analysis identified another possible oxidative-stress resistance protein (HP0630) that was up-regulated in the double mutant. However, the transcription start site of the HP0630 gene was the same for the double mutant as for the wild type. It appears that H. pylori can readily modulate the expression of other resistance factors as a compensatory response to loss of a major oxidative-stress resistance component.

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Gengnianchun, a Traditional Chinese Medicine, Enhances Oxidative Stress Resistance and Lifespan in Caenorhabditis elegans by Modulating daf-16/FOXO

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2017/8432306 ◽

2017 ◽

Vol 2017 ◽

pp. 1-10 ◽

Cited By ~ 8

Author(s):

Fanhui Meng ◽

Jun Li ◽

Wenjun Wang ◽

Yan Fu

Keyword(s):

Oxidative Stress ◽

Caenorhabditis Elegans ◽

Chinese Medicine ◽

Traditional Chinese Medicine ◽

Stress Resistance ◽

Transgenic Animals ◽

Wild Type ◽

Oxidative Stress Resistance ◽

C Elegans ◽

And Oxidative Stress

Objective. Gengnianchun (GNC), a traditional Chinese medicine (TCM), is primarily used to improve declining functions related to aging. In this study, we investigated its prolongevity and stress resistance properties and explored the associated regulatory mechanism using a Caenorhabditis elegans model. Methods. Wild-type C. elegans N2 was used for lifespan analysis and oxidative stress resistance assays. Transgenic animals were used to investigate pathways associated with antioxidative stress activity. The effects of GNC on levels of reactive oxygen species (ROS) and expression of specific genes were examined. Results. GNC-treated wild-type worms showed an increase in survival time under both normal and oxidative stress conditions. GNC decreased intracellular ROS levels by 67.95%. GNC significantly enhanced the oxidative stress resistance of several mutant strains, suggesting that the protective effect of GNC is independent of the function of these genes. However, the oxidative stress resistance effect of GNC was absent in worms with daf-16 mutation. We also found upregulation of daf-16 downstream targets including sod-3 and mtl-1. Conclusions. Our findings suggest that GNC extends the lifespan of C. elegans and enhances its resistance to oxidative stress via a daf-16/FOXO-dependent pathway. This study also provides a feasible method for screening the biological mechanisms of TCMs.

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Catalase (KatA) and Alkyl Hydroperoxide Reductase (AhpC) Have Compensatory Roles in Peroxide Stress Resistance and Are Required for Survival, Persistence, and Nasal Colonization in Staphylococcus aureus

Journal of Bacteriology ◽

10.1128/jb.01524-06 ◽

2006 ◽

Vol 189 (3) ◽

pp. 1025-1035 ◽

Cited By ~ 161

Author(s):

Kate Cosgrove ◽

Graham Coutts ◽

Ing-Marie Jonsson ◽

Andrej Tarkowski ◽

John F. Kokai-Kun ◽

...

Keyword(s):

Oxidative Stress ◽

Staphylococcus Aureus ◽

Stress Resistance ◽

Catalase Activity ◽

Metal Ion ◽

Hospital Environment ◽

Growth Defect ◽

Nasal Colonization ◽

Oxidative Stress Resistance ◽

Metal Ion Homeostasis

ABSTRACT Oxidative-stress resistance in Staphylococcus aureus is linked to metal ion homeostasis via several interacting regulators. In particular, PerR controls the expression of a regulon of genes, many of which encode antioxidants. Two PerR regulon members, ahpC (alkylhydroperoxide reductase) and katA (catalase), show compensatory regulation, with independent and linked functions. An ahpC mutation leads to increased H2O2 resistance due to greater katA expression via relief of PerR repression. Moreover, AhpC provides residual catalase activity present in a katA mutant. Mutation of both katA and ahpC leads to a severe growth defect under aerobic conditions in defined media (attributable to lack of catalase activity). This results in the inability to scavenge exogenous or endogenously produced H2O2, resulting in accumulation of H2O2 in the medium. This leads to DNA damage, the likely cause of the growth defect. Surprisingly, the katA ahpC mutant is not attenuated in two independent models of infection, which implies reduced oxygen availability during infection. In contrast, both AhpC and KatA are required for environmental persistence (desiccation) and nasal colonization. Thus, oxidative-stress resistance is an important factor in the ability of S. aureus to persist in the hospital environment and so contribute to the spread of human disease.

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Identification of Listeria monocytogenes genes contributing to oxidative stress resistance under conditions relevant to host infection

Infection and Immunity ◽

10.1128/iai.00700-20 ◽

2021 ◽

Author(s):

David R. Mains ◽

Samuel J. Eallonardo ◽

Nancy E. Freitag

Keyword(s):

Oxidative Stress ◽

Listeria Monocytogenes ◽

Virulence Factors ◽

Stress Resistance ◽

Mammalian Cells ◽

Bacterial Virulence ◽

Host Cells ◽

Physiological Adaptation ◽

Wild Type ◽

Oxidative Stress Resistance

The Gram-positive bacterium Listeria monocytogenes survives in environments ranging from the soil to the cytosol of infected host cells. Key to L. monocytogenes intracellular survival is the activation of PrfA, a transcriptional regulator that is required for the expression of multiple bacterial virulence factors. Mutations that constitutively activate prfA (prfA* mutations) result in high-level expression of multiple bacterial virulence factors as well as the physiological adaptation of L. monocytogenes for optimal replication within host cells. Here we demonstrate that L. monocytogenes prfA* mutants exhibit significantly enhanced resistance to oxidative stress in comparison to wild type strains. Transposon mutagenesis of L. monocytogenes prfA* strains resulted in the identification of three novel gene targets required for full oxidative stress resistance only in the context of PrfA activation. One gene, lmo0779, predicted to encode an uncharacterized protein, and two additional genes known as cbpA and ygbB, encoding a cyclic-di-AMP binding protein and a 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase respectively, contribute to the enhanced oxidative stress resistance of prfA* strains while exhibiting no significant contribution in wild type L. monocytogenes. Transposon inactivation of cbpA and lmo0779 in a prfA* background led to reduced virulence in the liver of infected mice. These results indicate that L. monocytogenes calls upon specific bacterial factors for stress resistance in the context of PrfA activation and thus under conditions favorable for bacterial replication within infected mammalian cells.

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