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  • 1
    In: BMC Genomics, Springer Science and Business Media LLC, Vol. 17, No. 1 ( 2016-12)
    Materialart: Online-Ressource
    ISSN: 1471-2164
    Sprache: Englisch
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2016
    ZDB Id: 2041499-7
    SSG: 12
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    In: mBio, American Society for Microbiology, Vol. 2, No. 1 ( 2011-03)
    Kurzfassung: The severe diarrheal disease cholera is caused by the bacterium Vibrio cholerae , which can be transmitted to humans from the aquatic environment. Factors that affect V. cholerae in the environment can impact the occurrence of cholera outbreaks; one of these factors is thought to be the presence of bacterial viruses, or bacteriophages. Bacteriophages that prey on V. cholerae in the environment, and potentially in humans, have not been extensively genetically characterized. Here, we isolated and sequenced the genomes of bacteriophages from cholera patient stool samples collected over a 10-year period in Dhaka, Bangladesh, a region that suffers from regular cholera outbreaks. We describe a unique bacteriophage present in all samples, infer its evolution by sequencing multiple isolates from different patients over time, and identify the host receptor that shows that the bacteriophage specifically predates the serogroup of V. cholerae responsible for the majority of disease occurrences.
    Materialart: Online-Ressource
    ISSN: 2161-2129 , 2150-7511
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2011
    ZDB Id: 2557172-2
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    MDPI AG ; 2016
    In:  International Journal of Environmental Research and Public Health Vol. 13, No. 2 ( 2016-02-03), p. 187-
    In: International Journal of Environmental Research and Public Health, MDPI AG, Vol. 13, No. 2 ( 2016-02-03), p. 187-
    Materialart: Online-Ressource
    ISSN: 1660-4601
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2016
    ZDB Id: 2175195-X
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    Springer Science and Business Media LLC ; 2012
    In:  BMC Genomics Vol. 13, No. 1 ( 2012-12)
    In: BMC Genomics, Springer Science and Business Media LLC, Vol. 13, No. 1 ( 2012-12)
    Kurzfassung: Porphyromonas gingivalis is a Gram-negative anaerobic bacterium associated with periodontal disease onset and progression. Genetic tools for the manipulation of bacterial genomes allow for in-depth mechanistic studies of metabolism, physiology, interspecies and host-pathogen interactions. Analysis of the essential genes, protein-coding sequences necessary for survival of P. gingivalis by transposon mutagenesis has not previously been attempted due to the limitations of available transposon systems for the organism. We adapted a Mariner transposon system for mutagenesis of P. gingivalis and created an insertion mutant library. By analyzing the location of insertions using massively-parallel sequencing technology we used this mutant library to define genes essential for P. gingivalis survival under in vitro conditions. Results In mutagenesis experiments we identified 463 genes in P. gingivalis strain ATCC 33277 that are putatively essential for viability in vitro . Comparing the 463 P. gingivalis essential genes with previous essential gene studies, 364 of the 463 are homologues to essential genes in other species; 339 are shared with more than one other species. Twenty-five genes are known to be essential in P. gingivalis and B. thetaiotaomicron only. Significant enrichment of essential genes within Cluster of Orthologous Groups ‘D’ (cell division), ‘I’ (lipid transport and metabolism) and ‘J’ (translation/ribosome) were identified. Previously, the P. gingivalis core genome was shown to encode 1,476 proteins out of a possible 1,909; 434 of 463 essential genes are contained within the core genome. Thus, for the species P. gingivalis twenty-two, seventy-seven and twenty-three percent of the genome respectively are devoted to essential, core and accessory functions. Conclusions A Mariner transposon system can be adapted to create mutant libraries in P. gingivalis amenable to analysis by next-generation sequencing technologies. In silico analysis of genes essential for in vitro growth demonstrates that although the majority are homologous across bacterial species as a whole, species and strain-specific subsets are apparent. Understanding the putative essential genes of P. gingivalis will provide insights into metabolic pathways and niche adaptations as well as clinical therapeutic strategies.
    Materialart: Online-Ressource
    ISSN: 1471-2164
    Sprache: Englisch
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2012
    ZDB Id: 2041499-7
    SSG: 12
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    American Society for Microbiology ; 2006
    In:  Infection and Immunity Vol. 74, No. 6 ( 2006-06), p. 3633-3642
    In: Infection and Immunity, American Society for Microbiology, Vol. 74, No. 6 ( 2006-06), p. 3633-3642
    Kurzfassung: Differences in whole-genome expression patterns between the classical and El Tor biotypes of Vibrio cholerae O1 were determined under conditions that induce virulence gene expression in the classical biotype. A total of 524 genes (13.5% of the genome) were found to be differentially expressed in the two biotypes. The expression of genes encoding proteins required for biofilm formation, chemotaxis, and transport of amino acids, peptides, and iron was higher in the El Tor biotype. These gene expression differences may contribute to the enhanced survival capacity of the El Tor biotype in environmental reservoirs. The expression of genes encoding virulence factors was higher in the classical than in the El Tor biotype. In addition, the vieSAB genes, which were originally identified as regulators of ctxA transcription, were expressed at a fivefold higher level in the classical biotype. We determined the VieA regulon in both biotypes by transcriptome comparison of wild-type and vieA deletion mutant strains. VieA predominantly regulates gene expression in the classical biotype; 401 genes (10.3% of the genome), including those encoding proteins required for virulence, exopolysaccharide biosynthesis, and flagellum production as well as those regulated by σ E , are differentially expressed in the classical vieA deletion mutant. In contrast, only five genes were regulated by VieA in the El Tor biotype. A large fraction (20.8%) of the genes that are differentially expressed in the classical versus the El Tor biotype are controlled by VieA in the classical biotype. Thus, VieA is a major regulator of genes in the classical biotype under virulence gene-inducing conditions.
    Materialart: Online-Ressource
    ISSN: 0019-9567 , 1098-5522
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2006
    ZDB Id: 1483247-1
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  • 6
    In: Infection and Immunity, American Society for Microbiology, Vol. 82, No. 6 ( 2014-06), p. 2356-2367
    Kurzfassung: Hypervirulent (hypermucoviscous) Klebsiella pneumoniae (hvKP) strains are an emerging variant of “classical” K. pneumoniae (cKP) that cause organ and life-threatening infection in healthy individuals. An understanding of hvKP-specific virulence mechanisms that enabled evolution from cKP is limited. Observations by our group and previously published molecular epidemiologic data led us to hypothesize that hvKP strains produced more siderophores than cKP strains and that this trait enhanced hvKP virulence. Quantitative analysis of 12 hvKP strains in iron-poor minimal medium or human ascites fluid showed a significant and distinguishing 6- to 10-fold increase in siderophore production compared to that for 14 cKP strains. Surprisingly, high-pressure liquid chromatography (HPLC)-mass spectrometry and characterization of the hvKP strains hvKP1, A1142, and A1365 and their isogenic aerobactin-deficient (Δ iucA ) derivatives established that aerobactin accounted for the overwhelming majority of increased siderophore production and that this was not due to gene copy number. Further, aerobactin was the primary factor in conditioned medium that enhanced the growth/survival of hvKP1 in human ascites fluid. Importantly the ex vivo growth/survival of hvKP1 Δ iucA was significantly less than that of hvKP1 in human ascites fluid, and the survival of outbred CD1 mice challenged subcutaneously or intraperitoneally with hvKP1 was significantly less than that of mice challenged with hvKP1 Δ iucA . The lowest subcutaneous and intraperitoneal challenge inocula of 3 × 10 2 and 3.2 × 10 1 CFU, respectively, resulted in 100% mortality, demonstrating the virulence of hvKP1 and its ability to cause infection at a low dose. These data strongly support that aerobactin accounts for increased siderophore production in hvKP compared to cKP (a potential defining trait) and is an important virulence factor.
    Materialart: Online-Ressource
    ISSN: 0019-9567 , 1098-5522
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2014
    ZDB Id: 1483247-1
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Online-Ressource
    Online-Ressource
    American Society for Microbiology ; 2014
    In:  Infection and Immunity Vol. 82, No. 6 ( 2014-06), p. 2434-2447
    In: Infection and Immunity, American Society for Microbiology, Vol. 82, No. 6 ( 2014-06), p. 2434-2447
    Kurzfassung: Vibrio cholerae is the causative agent of the acute diarrheal disease of cholera. Innate immune responses to V. cholerae are not a major cause of cholera pathology, which is characterized by severe, watery diarrhea induced by the action of cholera toxin. Innate responses may, however, contribute to resolution of infection and must be required to initiate adaptive responses after natural infection and oral vaccination. Here we investigated whether a well-established infant mouse model of cholera can be used to observe an innate immune response. We also used a vaccination model in which immunized dams protect their pups from infection through breast milk antibodies to investigate innate immune responses after V. cholerae infection for pups suckled by an immune dam. At the peak of infection, we observed neutrophil recruitment accompanied by induction of KC, macrophage inflammatory protein 2 (MIP-2), NOS-2, interleukin-6 (IL-6), and IL-17a. Pups suckled by an immunized dam did not mount this response. Accessory toxins RtxA and HlyA played no discernible role in neutrophil recruitment in a wild-type background. The innate response to V. cholerae deleted for cholera toxin-encoding phage (CTXϕ) and part of rtxA was significantly reduced, suggesting a role for CTXϕ-carried genes or for RtxA in the absence of cholera toxin (CTX). Two extracellular V. cholerae DNases were not required for neutrophil recruitment, but DNase-deficient V. cholerae caused more clouds of DNA in the intestinal lumen, which appeared to be neutrophil extracellular traps (NETs), suggesting that V. cholerae DNases combat NETs. Thus, the infant mouse model has hitherto unrecognized utility for interrogating innate responses to V. cholerae infection.
    Materialart: Online-Ressource
    ISSN: 0019-9567 , 1098-5522
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2014
    ZDB Id: 1483247-1
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Online-Ressource
    Online-Ressource
    American Society for Microbiology ; 2015
    In:  Infection and Immunity Vol. 83, No. 3 ( 2015-03), p. 1199-1209
    In: Infection and Immunity, American Society for Microbiology, Vol. 83, No. 3 ( 2015-03), p. 1199-1209
    Kurzfassung: Two-component systems play important roles in the physiology of many bacterial pathogens. Vibrio cholerae 's CarRS two-component regulatory system negatively regulates expression of vps ( Vibrio polysaccharide) genes and biofilm formation. In this study, we report that CarR confers polymyxin B resistance by positively regulating expression of the almEFG genes, whose products are required for glycine and diglycine modification of lipid A. We determined that CarR directly binds to the regulatory region of the almEFG operon. Similarly to a carR mutant, strains lacking almE , almF , and almG exhibited enhanced polymyxin B sensitivity. We also observed that strains lacking almE or the almEFG operon have enhanced biofilm formation. Our results reveal that CarR regulates biofilm formation and antimicrobial peptide resistance in V. cholerae .
    Materialart: Online-Ressource
    ISSN: 0019-9567 , 1098-5522
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2015
    ZDB Id: 1483247-1
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  • 9
    Online-Ressource
    Online-Ressource
    American Society for Microbiology ; 2004
    In:  Infection and Immunity Vol. 72, No. 4 ( 2004-04), p. 2405-2407
    In: Infection and Immunity, American Society for Microbiology, Vol. 72, No. 4 ( 2004-04), p. 2405-2407
    Kurzfassung: Acid adaptation has previously been shown to increase the infectivity of Vibrio cholerae in the infant mouse model. To better understand this phenomenon, we monitored the spatial distribution and temporal changes in the ratios of acid-adapted cells to unadapted V. cholerae cells in the small intestine, as well as the timing of virulence factor expression. We found that the competitive advantage afforded by acid adaptation does not become manifest until greater than 3 h postinfection; thus, acid adaptation does not increase V. cholerae passage through the gastric acid barrier. Additionally, acid-adapted and unadapted V. cholerae cells colonize the same sections of the small intestine and show similar kinetics of transcriptional induction of the virulence genes tcpA and ctxA. These studies suggest that the increased infectivity of acid-adapted V. cholerae is due to a more rapid onset of multiplication and/or to an increased multiplication rate within the infant mouse intestine.
    Materialart: Online-Ressource
    ISSN: 0019-9567 , 1098-5522
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2004
    ZDB Id: 1483247-1
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Online-Ressource
    Online-Ressource
    American Society for Microbiology ; 2006
    In:  Infection and Immunity Vol. 74, No. 4 ( 2006-04), p. 2072-2079
    In: Infection and Immunity, American Society for Microbiology, Vol. 74, No. 4 ( 2006-04), p. 2072-2079
    Kurzfassung: Vibrio cholerae is a highly motile organism that secretes a Zn-dependent metalloprotease, hemagglutinin/protease (HapA). HapA has been shown to have mucinase activity and contribute to the reactogenicity of live vaccine candidates, but its role in cholera pathogenesis is not yet clear. The contribution of motility to pathogenesis is not fully understood, since conflicting results have been obtained with different strains, mutants, and animal models. The objective of this work was to determine the contribution of HapA and motility to the pathogenesis of El Tor biotype cholera. To this end we constructed isogenic motility ( motY ) and mucinase ( hapA ) single and double mutants of an El Tor biotype V. cholerae strain. Mutants were characterized for the expression of major virulence factors in vitro and in vivo. The motility mutant showed a remarkable increase in cholera toxin (CT), toxin coregulated pilus major subunit (TcpA), and HapA production in vitro. Increased TcpA and CT production could be explained by increased transcription of tcpA , ctxA , and toxT . No effect was detected on the transcription of hapA in the motility mutant. The sodium ionophore monensin diminished production of HapA in the parent but not in the motility mutant. Phenamil, a specific inhibitor of the flagellar motor, diminished CT production in the wild-type and motY strains. The hapA mutant showed increased binding to mucin. In contrast, the motY mutation diminished adherence to biotic and abiotic surfaces including mucin. Lack of HapA did not affect colonization in the suckling mouse model. The motility and mucinase defects did not prevent induction of ctxA and tcpA in the mouse intestine as measured by recombinase-based in vivo expression technology. Analysis of mutants in the rabbit ileal loop model showed that both V. cholerae motility and HapA were necessary for full expression of enterotoxicity.
    Materialart: Online-Ressource
    ISSN: 0019-9567 , 1098-5522
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2006
    ZDB Id: 1483247-1
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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