The Experts below are selected from a list of 3984 Experts worldwide ranked by ideXlab platform
Pierre Cornelis - One of the best experts on this subject based on the ideXlab platform.
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Aerobic Denitration of 2,4,6-Trinitrotoluene in the Presence of Phenazine Compounds and Reduced Pyridine Nucleotides
2012Co-Authors: Ben Stenuit, Pierre Cornelis, Guillaume Lamblin, Spiros N. AgathosAbstract:Phenazine-containing spent culture supernatants of Pseudomonas aeruginosa concentrated with a C18 solid-phase extraction cartridge initiate NAD(P)H-dependent denitration of 2,4,6-trinitrotoluene (TNT). In this study, TNT denitration was investigated under aerobic conditions using two phenazine secondary metabolites excreted by P. aeruginosa, Pyocyanin (Py) and its precursor phenazine-1-carboxylic acid (PCA), and two chemically synthesized Pyocyanin analogs, phenazine methosulfate (PMS+) and phenazine ethosulfate (PES+). The biomimetic Py/NAD(P)H/O2 system was characterized and found to extensively denitrate TNT in unbuffered aqueous solution with minor production of toxic aminoaromatic derivatives. To a much lesser extent, TNT denitration was also observed with PMS+ and PES+ in the presence of NAD(P)H. No TNT denitration was detected with the biomimetic PCA/NAD(P)H/O2 system. Electron paramagnetic resonance (EPR) spectroscopy analysis of the biomimetic Py/NAD(P)H/O2 system revealed the generation of superoxide radical anions (O2•–). In vitro TNT degradation experiments in the presence of specific inhibitors of reactive oxygen species suggest a nucleophilic attack of superoxide radical anion followed by TNT denitration through an as yet unknown mechanism. The results of this research confirm the high functional versatility of the redox-active metabolite Pyocyanin and the susceptibility of aromatic compounds bearing electron-withdrawing substituents, such as nitro groups, to superoxide-driven nucleophilic attack
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the pseudomonas aeruginosa oxidative stress regulator oxyr influences production of Pyocyanin and rhamnolipids protective role of Pyocyanin
Microbiology, 2010Co-Authors: Tiffany Vinckx, Qing Wei, Sandra Matthijs, Pierre CornelisAbstract:The LysR-type transcriptional regulator (LTTR) OxyR orchestrates the defence of the opportunistic pathogen Pseudomonas aeruginosa against reactive oxygen species. In previous work we also demonstrated that OxyR is needed for the utilization of the ferrisiderophore pyoverdine, stressing the importance of this regulator. Here, we show that an oxyR mutant is unable to swarm on agar plates, probably as a consequence of absence of production of rhamnolipid surfactant molecules. Another obvious phenotypic change was the increased production of the phenazine redox-active molecule Pyocyanin in the oxyR mutant. As already described, the oxyR mutant could not grow in LB medium, unless high numbers of cells (.10 8 ml ”1 ) were inoculated. However, its growth in Pseudomonas P agar (King’s A), a medium inducing Pyocyanin production, was like that of the wild-type, suggesting a protective action of this redox-active phenazine compound. This was confirmed by the restoration of the capacity to grow in LB medium upon addition of pure Pyocyanin. Although both rhamnolipid and Pyocyanin production are controlled by quorum sensing, no obvious changes were observed in the production of N-acylhomoserine lactones or the Pseudomonas quinolone signal (PQS). Complementation of rhamnolipid production and motility, and restoration of normal Pyocyanin levels, was only possible when the oxyR gene was in single copy, while Pyocyanin levels were increased when oxyR was present in a multicopy vector. Conversely, plating efficiency was increased only when the oxyR gene was present in multicopy, but not when in single copy in the chromosome, due to lower expression of oxyR compared with the wild-type, suggesting that some phenotypes are differently affected in function to the levels of OxyR molecules in the cell. Analysis of transcripts of oxidative stress-response enzymes showed a strong decrease of katB, ahpC and ahpB expression in the oxyR mutant grown in LB, but this was not the case when the mutant was grown on P agar, suggesting that the OxyR dependency for the transcription of these genes is not total.
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redox active Pyocyanin secreted by pseudomonas aeruginosa 7nsk2 triggers systemic resistance to magnaporthe grisea but enhances rhizoctonia solani susceptibility in rice
Molecular Plant-microbe Interactions, 2006Co-Authors: David De Vleesschauwer, Pierre CornelisAbstract:Pseudomonas aeruginosa 7NSK2 induces resistance in dicots through a synergistic interaction of the phenazine Pyocyanin and the salicylic acid-derivative pyochelin. Root inoculation of the monocot model rice with 7NSK2 partially protected leaves against blast disease (Magnaporthe grisea) but failed to consistently reduce sheath blight (Rhizoctonia solani). Only mutations interfering with Pyocyanin production led to a significant decrease in induced systemic resistance (ISR) to M. grisea, and in trans complementation for Pyocyanin production restored the ability to elicit ISR. Intriguingly, Pyocyanin-deficient mutants, unlike the wild type, triggered ISR against R. solani. Hence, bacterial Pyocyanin plays a differential role in 7NSK2-mediated ISR in rice. Application of purified Pyocyanin to hydroponically grown rice seedlings increased H2O2 levels locally on the root surface as well as a biphasic H2O2 generation pattern in distal leaves. Co-application of Pyocyanin and the antioxidant sodium ascorbate alle...
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redox active Pyocyanin secreted by pseudomonas aeruginosa 7nsk2 triggers systemic resistance to magnaporthe grisea but enhances rhizoctonia solani susceptibility in rice
Molecular Plant-microbe Interactions, 2006Co-Authors: David De Vleesschauwer, Pierre CornelisAbstract:Pseudomonas aeruginosa 7NSK2 induces resistance in dicots through a synergistic interaction of the phenazine Pyocyanin and the salicylic acid-derivative pyochelin. Root inoculation of the monocot model rice with 7NSK2 partially protected leaves against blast disease (Magnaporthe grisea) but failed to consistently reduce sheath blight (Rhizoctonia solani). Only mutations interfering with Pyocyanin production led to a significant decrease in induced systemic resistance (ISR) to M. grisea, and in trans complementation for Pyocyanin production restored the ability to elicit ISR. Intriguingly, Pyocyanin-deficient mutants, unlike the wild type, triggered ISR against R. solani. Hence, bacterial Pyocyanin plays a differential role in 7NSK2-mediated ISR in rice. Application of purified Pyocyanin to hydroponically grown rice seedlings increased H202 levels locally on the root surface as well as a biphasic H202 generation pattern in distal leaves. Co-application of Pyocyanin and the antioxidant sodium ascorbate alleviated the opposite effects of Pyocyanin on rice blast and sheath blight development, suggesting that the differential effectiveness of Pyocyanin with respect to 7NSK2-triggered ISR is mediated by transiently elevated H202 levels in planta. The cumulative results suggest that reactive oxygen species act as a double-edged sword in the interaction of rice with the hemibiotroph M. grisea and the necrotroph R. solani.
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Pyocyanin production by pseudomonas aeruginosa induces neutrophil apoptosis and impairs neutrophil mediated host defenses in vivo
Journal of Immunology, 2005Co-Authors: Lucy Allen, Pierre Cornelis, Theresa Pattery, David H Dockrell, Daniel G Lee, Paul G Hellewell, Moira K B WhyteAbstract:Clearance of neutrophils from inflamed sites is critical for resolution of inflammation, but pathogen-driven neutrophil apoptosis can impair host defenses. We previously showed that Pyocyanin, a phenazine toxic metabolite produced by Pseudomonas aeruginosa, accelerates neutrophil apoptosis in vitro. We compared wild-type and Pyocyanin-deficient strains of P. aeruginosa in a murine model of acute pneumonia. Intratracheal instillation of either strain of P. aeruginosa caused a rapid increase in bronchoalveolar lavage neutrophil counts up to 18 h after infection. In wild-type infection, neutrophil numbers then declined steadily, whereas neutrophil numbers increased up to 48 h in mice infected with Pyocyanin-deficient P. aeruginosa. In keeping with these differences, Pyocyanin production was associated with reduced bacterial clearance from the lungs. Neutrophil apoptosis was increased in mice infected with wild-type compared with the phenazine-deficient strain or two further strains that lack Pyocyanin production, but produce other phenazines. Concentrations of potent neutrophil chemokines (MIP-2, KC) and cytokines (IL-6, IL-1beta) were significantly lower in wild-type compared with phenazine-deficient strain-infected mice at 18 h. We conclude that Pyocyanin production by P. aeruginosa suppresses the acute inflammatory response by pathogen-driven acceleration of neutrophil apoptosis and by reducing local inflammation, and that this is advantageous for bacterial survival.
Moira K B Whyte - One of the best experts on this subject based on the ideXlab platform.
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Pyocyanin production by pseudomonas aeruginosa induces neutrophil apoptosis and impairs neutrophil mediated host defenses in vivo
Journal of Immunology, 2005Co-Authors: Lucy Allen, Pierre Cornelis, Theresa Pattery, David H Dockrell, Daniel G Lee, Paul G Hellewell, Moira K B WhyteAbstract:Clearance of neutrophils from inflamed sites is critical for resolution of inflammation, but pathogen-driven neutrophil apoptosis can impair host defenses. We previously showed that Pyocyanin, a phenazine toxic metabolite produced by Pseudomonas aeruginosa, accelerates neutrophil apoptosis in vitro. We compared wild-type and Pyocyanin-deficient strains of P. aeruginosa in a murine model of acute pneumonia. Intratracheal instillation of either strain of P. aeruginosa caused a rapid increase in bronchoalveolar lavage neutrophil counts up to 18 h after infection. In wild-type infection, neutrophil numbers then declined steadily, whereas neutrophil numbers increased up to 48 h in mice infected with Pyocyanin-deficient P. aeruginosa. In keeping with these differences, Pyocyanin production was associated with reduced bacterial clearance from the lungs. Neutrophil apoptosis was increased in mice infected with wild-type compared with the phenazine-deficient strain or two further strains that lack Pyocyanin production, but produce other phenazines. Concentrations of potent neutrophil chemokines (MIP-2, KC) and cytokines (IL-6, IL-1beta) were significantly lower in wild-type compared with phenazine-deficient strain-infected mice at 18 h. We conclude that Pyocyanin production by P. aeruginosa suppresses the acute inflammatory response by pathogen-driven acceleration of neutrophil apoptosis and by reducing local inflammation, and that this is advantageous for bacterial survival.
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induction of neutrophil apoptosis by the pseudomonas aeruginosa exotoxin Pyocyanin a potential mechanism of persistent infection
Journal of Immunology, 2002Co-Authors: Lynne R Usher, Roderick Lawson, I Geary, C J Taylor, Colin D Bingle, G W Taylor, Moira K B WhyteAbstract:Pseudomonas aeruginosa colonizes and infects human tissues, although the mechanisms by which the organism evades the normal, predominantly neutrophilic, host defenses are unclear. Phenazine products of P. aeruginosa can induce death in Caenorhabditis elegans. We hypothesized that phenazines induce death of human neutrophils, and thus impair neutrophil-mediated bacterial killing. We investigated the effects of two phenazines, Pyocyanin and 1-hydroxyphenazine, upon apoptosis of neutrophils in vitro. Pyocyanin induced a concentration- and time-dependent acceleration of neutrophil apoptosis, with 50 microM Pyocyanin causing a 10-fold induction of apoptosis at 5 h (p < 0.001), a concentration that has been documented in sputum from patients colonized with P. aeruginosa. 1-hydroxyphenazine was without effect. In contrast to its rapid induction of neutrophil apoptosis, Pyocyanin did not induce significant apoptosis of monocyte-derived macrophages or airway epithelial cells at time points up to 24 h. Comparison of wild-type and phenazine-deleted strains of P. aeruginosa showed a highly significant reduction in neutrophil killing by the phenazine-deleted strain. In clinical isolates of P. aeruginosa Pyocyanin production was associated with a proapoptotic effect upon neutrophils in culture. Pyocyanin-induced neutrophil apoptosis was not delayed either by treatment with LPS, a powerfully antiapoptotic bacterial product, or in neutrophils from cystic fibrosis patients. Pyocyanin-induced apoptosis was associated with rapid and sustained generation of reactive oxygen intermediates and subsequent reduction of intracellular cAMP. Treatment of neutrophils with either antioxidants or synthetic cAMP analogues significantly abrogated Pyocyanin-induced apoptosis. We conclude that Pyocyanin-induced neutrophil apoptosis may be a clinically important mechanism of persistence of P. aeruginosa in human tissue.
Romana Jarosova - One of the best experts on this subject based on the ideXlab platform.
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inkjet printed carbon nanotube electrodes for measuring Pyocyanin and uric acid in a wound fluid simulant and culture media
Analytical Chemistry, 2019Co-Authors: Romana Jarosova, Sandra Mcclure, Margaret Gajda, Milica Jovic, Hubert H Girault, Andreas Lesch, Michael M Maiden, Christopher M Waters, Greg M SwainAbstract:Polyacrylamide-coated, carbon nanotube (PA/CNT) electrodes were prepared by an inkjet printing process and used to measure Pyocyanin and uric acid in a wound fluid simulant at 37 °C. These two mole...
Greg M Swain - One of the best experts on this subject based on the ideXlab platform.
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inkjet printed carbon nanotube electrodes for measuring Pyocyanin and uric acid in a wound fluid simulant and culture media
Analytical Chemistry, 2019Co-Authors: Romana Jarosova, Sandra Mcclure, Margaret Gajda, Milica Jovic, Hubert H Girault, Andreas Lesch, Michael M Maiden, Christopher M Waters, Greg M SwainAbstract:Polyacrylamide-coated, carbon nanotube (PA/CNT) electrodes were prepared by an inkjet printing process and used to measure Pyocyanin and uric acid in a wound fluid simulant at 37 °C. These two mole...
David De Vleesschauwer - One of the best experts on this subject based on the ideXlab platform.
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redox active Pyocyanin secreted by pseudomonas aeruginosa 7nsk2 triggers systemic resistance to magnaporthe grisea but enhances rhizoctonia solani susceptibility in rice
Molecular Plant-microbe Interactions, 2006Co-Authors: David De Vleesschauwer, Pierre CornelisAbstract:Pseudomonas aeruginosa 7NSK2 induces resistance in dicots through a synergistic interaction of the phenazine Pyocyanin and the salicylic acid-derivative pyochelin. Root inoculation of the monocot model rice with 7NSK2 partially protected leaves against blast disease (Magnaporthe grisea) but failed to consistently reduce sheath blight (Rhizoctonia solani). Only mutations interfering with Pyocyanin production led to a significant decrease in induced systemic resistance (ISR) to M. grisea, and in trans complementation for Pyocyanin production restored the ability to elicit ISR. Intriguingly, Pyocyanin-deficient mutants, unlike the wild type, triggered ISR against R. solani. Hence, bacterial Pyocyanin plays a differential role in 7NSK2-mediated ISR in rice. Application of purified Pyocyanin to hydroponically grown rice seedlings increased H2O2 levels locally on the root surface as well as a biphasic H2O2 generation pattern in distal leaves. Co-application of Pyocyanin and the antioxidant sodium ascorbate alle...
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redox active Pyocyanin secreted by pseudomonas aeruginosa 7nsk2 triggers systemic resistance to magnaporthe grisea but enhances rhizoctonia solani susceptibility in rice
Molecular Plant-microbe Interactions, 2006Co-Authors: David De Vleesschauwer, Pierre CornelisAbstract:Pseudomonas aeruginosa 7NSK2 induces resistance in dicots through a synergistic interaction of the phenazine Pyocyanin and the salicylic acid-derivative pyochelin. Root inoculation of the monocot model rice with 7NSK2 partially protected leaves against blast disease (Magnaporthe grisea) but failed to consistently reduce sheath blight (Rhizoctonia solani). Only mutations interfering with Pyocyanin production led to a significant decrease in induced systemic resistance (ISR) to M. grisea, and in trans complementation for Pyocyanin production restored the ability to elicit ISR. Intriguingly, Pyocyanin-deficient mutants, unlike the wild type, triggered ISR against R. solani. Hence, bacterial Pyocyanin plays a differential role in 7NSK2-mediated ISR in rice. Application of purified Pyocyanin to hydroponically grown rice seedlings increased H202 levels locally on the root surface as well as a biphasic H202 generation pattern in distal leaves. Co-application of Pyocyanin and the antioxidant sodium ascorbate alleviated the opposite effects of Pyocyanin on rice blast and sheath blight development, suggesting that the differential effectiveness of Pyocyanin with respect to 7NSK2-triggered ISR is mediated by transiently elevated H202 levels in planta. The cumulative results suggest that reactive oxygen species act as a double-edged sword in the interaction of rice with the hemibiotroph M. grisea and the necrotroph R. solani.
