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  • 1
    Language: English
    In: Current Opinion in Biotechnology, 2011, Vol.22(2), pp.200-210
    Description: ► Overview of 50 . Typhimurium transcriptomic studies dating from 2003 to 2010. ► Wealth of transcriptomics but few datasets from . Typhimurium infection. ► Genes that are highly expressed during infection often play a direct role in virulence. ► Lack of published studies of Salmonella gene expression during food processing. ► Understanding global gene expression datasets continues to be a challenge. The first decade of transcriptomic studies of serovar Typhimurium focused upon gene expression , and during the infection of mammalian cells. The published regulons and stimulons show that the three Type Three Secretion Systems of Typhimurium respond to a diverse range of environmental conditions, and are controlled by a hierarchy of regulatory proteins. The integration of generated transcriptomic data with global gene expression of Typhimurium during infection is beginning to yield valuable information. The coordinated regulation of Salmonella gene expression is a key process for survival, adaptation and virulence capacities of the pathogen.
    Keywords: Engineering
    ISSN: 0958-1669
    E-ISSN: 1879-0429
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  • 2
    Language: English
    In: Journal of Bacteriology, July, 2009, Vol.191(13-14), p.4605(10)
    Description: Salmonella enterica serovar Typhimurium is an intracellular pathogen that can survive and replicate within macrophages. One of the host defense mechanisms that Salmonella encounters during infection is the production of reactive oxygen species by the phagocyte NADPH oxidase. Among them, hydrogen peroxide ([H.sub.2][O.sub.2]) can diffuse across bacterial membranes and damage biomolecules. Genome analysis allowed us to identify five genes encoding [H.sub.2][O.sub.2] degrading enzymes: three catalases (KatE, KatG, and KatN) and two alkyl hydroperoxide reductases (AhpC and TsaA). Inactivation of the five cognate structural genes yielded the Hpx[F.sup.-] mutant, which exhibited a high sensitivity to exogenous [H.sub.2][O.sub.2] and a severe survival defect within macrophages. When the phagocyte NADPH oxidase was inhibited, its proliferation index increased 3.7-fold. Moreover, the overexpression of katG or tsaA in the Hpx[F.sup.-] background was sufficient to confer a proliferation index similar to that of the wild type in macrophages and a resistance to millimolar [H.sub.2][O.sub.2] in rich medium. The Hpx[F.sup.-] mutant also showed an attenuated virulence in a mouse model. These data indicate that Salmonella catalases and alkyl hydroperoxide reductases are required to degrade [H.sub.2][O.sub.2] and contribute to the virulence. This enzymatic redundancy highlights the evolutionary strategies developed by bacterial pathogens to survive within hostile environments.
    Keywords: Hydrogen Peroxide -- Physiological Aspects ; Salmonella -- Physiological Aspects ; Oxidative Stress -- Research ; Microbial Metabolism -- Research
    ISSN: 0021-9193
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 15 May 2012, Vol.109(20), pp.E1277-86
    Description: More than 50 y of research have provided great insight into the physiology, metabolism, and molecular biology of Salmonella enterica serovar Typhimurium (S. Typhimurium), but important gaps in our knowledge remain. It is clear that a precise choreography of gene expression is required for Salmonella infection, but basic genetic information such as the global locations of transcription start sites (TSSs) has been lacking. We combined three RNA-sequencing techniques and two sequencing platforms to generate a robust picture of transcription in S. Typhimurium. Differential RNA sequencing identified 1,873 TSSs on the chromosome of S. Typhimurium SL1344 and 13% of these TSSs initiated antisense transcripts. Unique findings include the TSSs of the virulence regulators phoP, slyA, and invF. Chromatin immunoprecipitation revealed that RNA polymerase was bound to 70% of the TSSs, and two-thirds of these TSSs were associated with σ(70) (including phoP, slyA, and invF) from which we identified the -10 and -35 motifs of σ(70)-dependent S. Typhimurium gene promoters. Overall, we corrected the location of important genes and discovered 18 times more promoters than identified previously. S. Typhimurium expresses 140 small regulatory RNAs (sRNAs) at early stationary phase, including 60 newly identified sRNAs. Almost half of the experimentally verified sRNAs were found to be unique to the Salmonella genus, and 〈20% were found throughout the Enterobacteriaceae. This description of the transcriptional map of SL1344 advances our understanding of S. Typhimurium, arguably the most important bacterial infection model.
    Keywords: Gene Expression Regulation, Bacterial -- Genetics ; RNA, Small Untranslated -- Genetics ; Regulatory Sequences, Ribonucleic Acid -- Genetics ; Salmonella Typhimurium -- Genetics ; Transcription, Genetic -- Genetics
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 4
    Language: English
    In: 2015, Vol.11(11), p.e1005262
    Description: Salmonella enterica serovar Typhimurium is arguably the world’s best-understood bacterial pathogen. However, crucial details about the genetic programs used by the bacterium to survive and replicate in macrophages have remained obscure because of the challenge of studying gene expression of intracellular pathogens during infection. Here, we report the use of deep sequencing (RNA-seq) to reveal the transcriptional architecture and gene activity of Salmonella during infection of murine macrophages, providing new insights into the strategies used by the pathogen to survive in a bactericidal immune cell. We characterized 3583 transcriptional start sites that are active within macrophages, and highlight 11 of these as candidates for the delivery of heterologous antigens from Salmonella vaccine strains. A majority (88%) of the 280 S . Typhimurium sRNAs were expressed inside macrophages, and SPI13 and SPI2 were the most highly expressed pathogenicity islands. We identified 31 S . Typhimurium genes that were strongly up-regulated inside macrophages but expressed at very low levels during in vitro growth. The SalComMac online resource allows the visualisation of every transcript expressed during bacterial replication within mammalian cells. This primary transcriptome of intra-macrophage S .-Typhimurium describes the transcriptional start sites and the transcripts responsible for virulence traits, and catalogues the sRNAs that may play a role in the regulation of gene expression during infection. ; The burden of Salmonellosis remains unacceptably high throughout the world and control measures have had limited success. Because Salmonella bacteria can be transmitted from the wider environment to animals and humans, the bacteria encounter diverse environments that include food, water, plant surfaces and the extracellular and intracellular phases of infection of eukaryotic hosts. An intricate transcriptional network has evolved to respond to a variety of environmental signals and control the “right time/ right place” expression of virulence genes. To understand how transcription is rewired during intracellular infection, we determined the primary transcriptome of Salmonella enterica serovar Typhimurium within murine macrophages. We report the coding genes, sRNAs and transcriptional start sites that are expressed within macrophages at 8 hours after infection, and use these to infer gene function. We identified gene promoters that are specifically expressed within macrophages and could drive the intracellular delivery of antigens by S . Typhimurium vaccine strains. These data contribute to our understanding of the mechanisms used by Salmonella to regulate virulence gene expression whilst replicating inside mammalian cells.
    Keywords: Research Article
    ISSN: 1553-7366
    E-ISSN: 1553-7374
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  • 5
    In: The Journal of Bacteriology, 2009, Vol. 191(14), p.4605
    Description: Salmonella enterica serovar Typhimurium is an intracellular pathogen that can survive and replicate within macrophages. One of the host defense mechanisms that Salmonella encounters during infection is the production of reactive oxygen species by the phagocyte NADPH oxidase. Among them, hydrogen peroxide (H...O...) can diffuse across bacterial membranes and damage biomolecules. Genome analysis allowed us to identify five genes encoding H...O... degrading enzymes: three catalases (KatE, KatG, and KatN) and two alkyl hydroperoxide reductases (AhpC and TsaA). Inactivation of the five cognate structural genes yielded the HpxF... mutant, which exhibited a high sensitivity to exogenous H...O... and a severe survival defect within macrophages. When the phagocyte NADPH oxidase was inhibited, its proliferation index increased 3.7-fold. Moreover, the overexpression of katG or tsaA in the HpxF... background was sufficient to confer a proliferation index similar to that of the wild type in macrophages and a resistance to millimolar H...O... in rich medium. The HpxF... mutant also showed an attenuated virulence in a mouse model. These data indicate that Salmonella catalases and alkyl hydroperoxide reductases are required to degrade H...O... and contribute to the virulence. This enzymatic redundancy highlights the evolutionary strategies developed by bacterial pathogens to survive within hostile environments. (ProQuest: ... denotes formulae/symbols omitted.)
    Keywords: Enzymes ; Salmonella ; Oxygen ; Genomics ; Genes ; Mutation ; Rodents;
    ISSN: 0021-9193
    ISSN: 00219193
    E-ISSN: 10985530
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  • 6
    Language: English
    In: Molecular microbiology, May 2011, Vol.80(3), pp.628-40
    Description: The oxidative burst produced by the NADPH oxidase (Phox) is an essential weapon used by host cells to eradicate engulfed pathogens. In Salmonella typhimurium, oxidative stress resistance has been previously proposed to be mediated by the pathogenicity island 2 type III secretion system (T3SS-2), periplasmic superoxide dismutases and cytoplasmic catalases/peroxidases. Here, we fused an OxyR-dependent promoter to the gfp to build the ahpC-gfp transcriptional fusion. This reporter was used to monitor hydrogen peroxide levels as sensed by Salmonella during the course of an infection. We showed that the expression of this fusion was under the exclusive control of reactive oxygen species produced by the host. The ahpC-gfp expression was noticeably modified in the absence of bacterial periplasmic superoxide dismutases or cytoplasmic catalases/peroxidases. Surprisingly, inactivation of the T3SS-2 had no effect on the ahpC-gfp expression. All together, these results led to a model in which Salmonella resistance relies on its arsenal of detoxifying enzymes to cope with Phox-mediated oxidative stress.
    Keywords: Respiratory Burst ; Hydrogen Peroxide -- Metabolism ; Macrophages -- Microbiology ; Reactive Oxygen Species -- Metabolism ; Salmonella Typhimurium -- Drug Effects
    ISSN: 0950382X
    E-ISSN: 1365-2958
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  • 7
    Language: English
    In: BBA - Molecular Basis of Disease, April 2011, Vol.1812(4), pp.423-430
    Description: Insulin resistance in type 2 diabetes (T2D) is associated with intramuscular lipid (IMCL) accumulation. To determine whether impaired lipid oxidation is involved in IMCL accumulation, we measured expression of genes involved in mitochondrial oxidative metabolism or biogenesis, mitochondrial content and palmitate beta-oxidation before and after palmitate overload (600 μM for 16 h), in myotubes derived from healthy subjects and obese T2D patients. Mitochondrial gene expression, content and network were not different between groups. Basal palmitate beta-oxidation was not affected in T2D myotubes, whereas after 16 h of palmitate pre-treatment, T2D myotubes in contrast to control myotubes, showed an inability to increase palmitate beta-oxidation ( 〈 0.05). Interestingly, acetyl-CoA carboxylase (ACC) phosphorylation was increased with a tendency for statistical significance after palmitate pre-treatment in control myotubes ( = 0.06) but not in T2D myotubes which can explain their inability to increase palmitate beta-oxidation after palmitate overload. To determine whether the activation of the AMP activated protein kinase (AMPK)-ACC pathway was able to decrease lipid content in T2D myotubes, cells were treated with AICAR and metformin. These AMPK activators had no effect on ACC and AMPK phosphorylation in T2D myotubes as well as on lipid content, whereas AICAR, but not metformin, increased AMPK phosphorylation in control myotubes. Interestingly, metformin treatment and mitochondrial inhibition by antimycin induced increased lipid content in control myotubes. We conclude that T2D myotubes display an impaired capacity to respond to metabolic stimuli. ► Mitochondrial content is normal in type 2 diabetic myotubes ► Palmitate oxidation is decreased in type 2 diabetic myotubes compared to control myotubes only in condition of lipid overload ► ACC inactivation by palmitate is impaired in type 2 diabetic myotubes ► AICAR and metformin treatments do not activate AMPK or decrease lipid content in type 2 diabetic myotubes ► Mitochondrial inhibition by antimycin or metformin induce an increase in lipid content in control myotubes.
    Keywords: Lipid Overflow ; Palmitate Beta-Oxidation ; Mitochondria ; Acetyl-Coa Carboxylase ; Amp Activated Protein Kinase ; Biology ; Chemistry
    ISSN: 0925-4439
    E-ISSN: 1879-260X
    E-ISSN: 18782434
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  • 8
    Language: English
    In: PLoS ONE, 2011, Vol.6(12), p.e28981
    Description: Permanent fatty acid translocase (FAT/)CD36 relocation has previously been shown to be related to abnormal lipid accumulation in the skeletal muscle of type 2 diabetic patients, however mechanisms responsible for the regulation of FAT/CD36 expression and localization are not well characterized in human skeletal muscle. ; Primary muscle cells derived from obese type 2 diabetic patients (OBT2D) and from healthy subjects (Control) were used to examine the regulation of FAT/CD36. We showed that compared to Control myotubes, FAT/CD36 was continuously cycling between intracellular compartments and the cell surface in OBT2D myotubes, independently of lipid raft association, leading to increased cell surface FAT/CD36 localization and lipid accumulation. Moreover, we showed that FAT/CD36 cycling and lipid accumulation were specific to myotubes and were not observed in reserve cells. However, in Control myotubes, the induction of FAT/CD36 membrane translocation by the activation of (AMP)-activated protein kinase (AMPK) pathway did not increase lipid accumulation. This result can be explained by the fact that pharmacological activation of AMPK leads to increased mitochondrial beta-oxidation in Control cells. ; Lipid accumulation in myotubes derived from obese type 2 diabetic patients arises from abnormal FAT/CD36 cycling while lipid accumulation in Control cells results from an equilibrium between lipid uptake and oxidation. As such, inhibiting FAT/CD36 cycling in the skeletal muscle of obese type 2 diabetic patients should be sufficient to diminish lipid accumulation.
    Keywords: Research Article ; Biology ; Medicine ; Diabetes And Endocrinology ; Genetics And Genomics ; Physiology ; Cell Biology ; Developmental Biology ; Biochemistry
    E-ISSN: 1932-6203
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  • 9
    Language: French
    Description: Les Formes Actives de l’Oxygène (FAO), molécules dérivées de l’oxygène, sont capables d’oxyder et d’endommager les macromolécules biologiques. Au cours de son cycle de vie, Salmonella typhimurium est exposée à des FAO provenant de deux sources : soit de son métabolisme aérobie, soit du macrophage, sa cellule hôte au cours de l’infection. Parmi les FAO existantes, l’H2O2 est l’une des plus néfastes. Au cours de ma thèse, j’ai étudié la contribution des catalases et des peroxyrédoxines dans le métabolisme et la virulence de S.typhimurium. Cinq enzymes ont ainsi été identifiées pour leur capacité à éliminer l’H2O2 : les catalases KatG, KatE, KatN et les peroxyrédoxines AhpCF et TsaA. Des tests de virulence ont également permis de montrer que ces enzymes participaient à l’établissement de la virulence.A l’aide d’une sonde moléculaire capable de détecter et de signaler l’H2O2, nous avons montré que S. typhimurium percevait cette FAO au cours de l’infection dans des macrophages murins. Ces résultats ont souligné l’importance des catalases et des peroxyrédoxines au cours de la vie intracellulaire de S. typhimurium. L’analyse du mutant DahpCF DtsaA Dtpx a également révélé que les peroxyrédoxines AhpCF, TsaA et Tpx contribuaient à la capacité de prolifération de la bactérie dans le macrophage. Enfin, l’étude des méthionine sulfoxyderéductases a montré que les caractéristiques d’un mutant DmsrA DmsrB étaient proches de celles de la souche sauvage. Les gènes msrA et msrB ont également été inactivés dans une souche dépourvue de katG, katE et ahpCF. Dans cette souche accumulant de l’H2O2endogène, la contribution de MsrA et MsrB devient évidente pour lutter contre les effets liés au stress oxydant. L’ensemble de ces travaux a permis d’identifier et de caractériser l’implication de systèmes antioxydants dans la virulence et le métabolisme de S. typhimurium. Reactive Oxygen Species (ROS), produced from molecular oxygen, can oxidize and damagebiological macromolecules. During its lifestyle, Salmonella typhimurium is submitted to ROScoming from two sources: its aerobic metabolism and its host cell upon infection, themacrophage. Among the ROS, H2O2 is one of the most toxic. In this work, the contribution ofcatalases and peroxiredoxins in the metabolism and the virulence of S. typhimurium wasstudied. Five enzymes are implied in H2O2 degradation, the catalases KatG, KatE, KatN andthe peroxiredoxins, AhpCF and TsaA. Virulence tests showed that these enzymes wereinvolved in virulence. Using a molecular probe able to detect and quantify H2O2, we showedthat S. typhimurium sensed H2O2 during infection in murine macrophages. These resultsunderlined the importance of catalases and peroxoxyredoxines for the intracellular life of S.typhimurium. Analysis of the mutant DahpCF DtsaA Dtpx revealed that the peroxiredoxinsAhpCF, TsaA and Tpx contributed to the bacterial proliferation inside macrophage. Finally,the study of the methionine sulfoxyde reductases showed that the phenotype of the mutantDmsrA DmsrB was related to the wild type strain. Then, msrA and msrB were inactivated in astrain deleted of katG, katE and ahpCF. In this strain impaired in H2O2 degradation, thecontribution of MsrA and MsrB to fight against oxidative stress effect is stronger. Altogether,these results allowed the identification and the contribution of antioxidant systems in S.typhimurium virulence and metabolism.
    Keywords: Salmonella Typhimurium ; Oxidative Stress ; Virulence ; Peroxyrédoxines
    Source: Networked Digital Library of Theses and Dissertations
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  • 10
    Language: English
    In: RNA Biology, 01 April 2012, Vol.9(4), pp.437-445
    Description: The combination of genomics and high-throughput cDNA sequencing technologies has facilitated the identification of many small RNAs (sRNAs) that play a central role in the post-transcriptional gene regulation of Salmonella enterica serovar Typhimurium. To date, most of the functionally characterized...
    Keywords: Salmonella Typhimurium ; Post-Transcriptional Regulation ; Srna ; Virulence ; Anatomy & Physiology
    ISSN: 1547-6286
    E-ISSN: 1555-8584
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