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  • 1
    Online Resource
    Online Resource
    Identification of an Orphan Response Regulator Required for the Virulence of Francisella spp. and Transcription of Pathogenicity Island Genes
    American Society for Microbiology ; 2007
    In:  Infection and Immunity Vol. 75, No. 7 ( 2007-07), p. 3305-3314
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 75, No. 7 ( 2007-07), p. 3305-3314
    Abstract: Francisella tularensis is a category A agent of biowarfare/biodefense. Little is known about the regulation of virulence gene expression in Francisella spp. Comparatively few regulatory factors exist in Francisella , including those belonging to two-component systems (TCS). However, orphan members of typical TCS can be identified. To determine if orphan TCS members affect Francisella gene expression, a gene encoding a product with high similarity to the Salmonella PmrA response regulator (FTT1557c/FNU0663.2) was deleted in Francisella novicida (a model organism for F. tularensis ). The F. novicida pmrA mutant was defective in survival/growth within human and murine macrophage cell lines and was 100% defective in virulence in mice at a dose of up to 10 8 CFU. In addition, the mutant strain demonstrated increased susceptibility to antimicrobial peptide killing, but no differences were observed between the lipid A of the mutant and the parental strain, as has been observed with pmrA mutants of other microbes. The F. novicida pmrA mutant was 100% protective as a single-dose vaccine when challenge was with 10 6 CFU of F. novicida but did not protect against type A Schu S4 wild-type challenge. DNA microarray analysis identified 65 genes regulated by PmrA. The majority of these genes were located in the region surrounding pmrA or within the Francisella pathogenicity island (FPI). These FPI genes are also regulated by MglA, but MglA does not regulate pmrA , nor does PmrA regulate MglA. Thus, the orphan response regulator PmrA is an important factor in controlling virulence in F. novicida , and a pmrA mutant strain is an effective vaccine against homologous challenge.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00351-07
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2007
    detail.hit.zdb_id: 1483247-1
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  • 2
    Online Resource
    Online Resource
    Late acyltransferase genes lpxX and lpxL jointly contribute to the biological activities of Moraxella catarrhalis
    Microbiology Society ; 2013
    In:  Journal of Medical Microbiology Vol. 62, No. 6 ( 2013-06-01), p. 807-812
    Details
    In: Journal of Medical Microbiology, Microbiology Society, Vol. 62, No. 6 ( 2013-06-01), p. 807-812
    Abstract: Lipo-oligosaccharide (LOS) is a major surface component and virulence factor of the human respiratory pathogen Moraxella catarrhalis . Two late acyltransferase genes, lpxX and lpxL , have been identified involved in the incorporation of acyloxyacyl-linked secondary acyl chains into lipid A during M. catarrhalis LOS biosynthesis. In this study, a double mutant with a deletion of both the lpxX and lpxL genes in M. catarrhalis strain O35E was constructed and named O35ElpxXL. Structural analysis of lipid A showed that the O35ElpxXL mutant lacked two decanoic acids (10 : 0) and one dodecanoic (lauric) acid (12 : 0). In comparison with the O35E parental strain and the single mutants O35ElpxX and O35ElpxL, the double mutant O35ElpxXL displayed prominently decreased endotoxin content, reduced resistance to normal human serum and accelerated bacterial clearance at 0, 3 and 6 h after an aerosol challenge in a mouse model of bacterial pulmonary clearance. These results indicate that these two genes encoding late acyltransferases responsible for lipid A biosynthesis jointly contribute to the biological activities and pathogenicity of M. catarrhalis. The double mutant O35ElpxXL with dramatically reduced toxicity is proposed as a potential vaccine candidate against M. catarrhalis infections for further investigation.
    Type of Medium: Online Resource
    ISSN: 0022-2615 , 1473-5644
    URL: Article
    DOI: 10.1099/jmm.0.056846-0
    RVK:
    XA 55020
    Language: English
    Publisher: Microbiology Society
    Publication Date: 2013
    detail.hit.zdb_id: 2083944-3
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Modification of Lipooligosaccharide with Phosphoethanolamine by LptA in Neisseria meningitidis Enhances Meningococcal Adhesion to Human Endothelial and Epithelial Cells
    American Society for Microbiology ; 2008
    In:  Infection and Immunity Vol. 76, No. 12 ( 2008-12), p. 5777-5789
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 76, No. 12 ( 2008-12), p. 5777-5789
    Abstract: The lipooligosaccharide (LOS) of Neisseria meningitidis can be decorated with phosphoethanolamine (PEA) at the 4′ position of lipid A and at the O-3 and O-6 positions of the inner core of the heptose II residue. The biological role of PEA modification in N. meningitidis remains unclear. During the course of our studies to elucidate the pathogenicity of the ST-2032 (invasive) meningococcal clonal group, disruption of lptA , the gene that encodes the PEA transferase for 4′ lipid A, led to a approximately 10-fold decrease in N. meningitidis adhesion to four kinds of human endothelial and epithelial cell lines at an multiplicity of infection of 5,000. Complementation of the lptA gene in a Δ lptA mutant restored wild-type adherence. By matrix-assisted laser desorption ionization-time-of-flight mass spectrometry analysis, PEA was lost from the lipid A of the Δ lptA mutant compared to that of the wild-type strain. The effect of LptA on meningococcal adhesion was independent of other adhesins such as pili, Opc, Opa, and PilC but was inhibited by the presence of capsule. These results indicate that modification of LOS with PEA by LptA enhances meningococcal adhesion to human endothelial and epithelial cells in unencapsulated N. meningitidis .
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00676-08
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2008
    detail.hit.zdb_id: 1483247-1
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  • 4
    Online Resource
    Online Resource
    The MisR Response Regulator Is Necessary for Intrinsic Cationic Antimicrobial Peptide and Aminoglycoside Resistance in Neisseria gonorrhoeae
    American Society for Microbiology ; 2016
    In:  Antimicrobial Agents and Chemotherapy Vol. 60, No. 8 ( 2016-08), p. 4690-4700
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 60, No. 8 ( 2016-08), p. 4690-4700
    Abstract: During infection, the sexually transmitted pathogen Neisseria gonorrhoeae (the gonococcus) encounters numerous host-derived antimicrobials, including cationic antimicrobial peptides (CAMPs) produced by epithelial and phagocytic cells. CAMPs have both direct and indirect killing mechanisms and help link the innate and adaptive immune responses during infection. Gonococcal CAMP resistance is likely important for avoidance of host nonoxidative killing systems expressed by polymorphonuclear granulocytes (e.g., neutrophils) and intracellular survival. Previously studied gonococcal CAMP resistance mechanisms include modification of lipid A with phosphoethanolamine by LptA and export of CAMPs by the MtrCDE efflux pump. In the related pathogen Neisseria meningitidis , a two-component regulatory system (2CRS) termed MisR-MisS has been shown to contribute to the capacity of the meningococcus to resist CAMP killing. We report that the gonococcal MisR response regulator but not the MisS sensor kinase is involved in constitutive and inducible CAMP resistance and is also required for intrinsic low-level resistance to aminoglycosides. The 4- to 8-fold increased susceptibility of misR -deficient gonococci to CAMPs and aminoglycosides was independent of phosphoethanolamine decoration of lipid A and the levels of the MtrCDE efflux pump and seemed to correlate with a general increase in membrane permeability. Transcriptional profiling and biochemical studies confirmed that expression of lptA and mtrCDE was not impacted by the loss of MisR. However, several genes encoding proteins involved in membrane integrity and redox control gave evidence of being MisR regulated. We propose that MisR modulates the levels of gonococcal susceptibility to antimicrobials by influencing the expression of genes involved in determining membrane integrity.
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.00823-16
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2016
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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  • 5
    Online Resource
    Online Resource
    Phosphoglucomutase of Yersinia pestis Is Required for Autoaggregation and Polymyxin B Resistance
    American Society for Microbiology ; 2010
    In:  Infection and Immunity Vol. 78, No. 3 ( 2010-03), p. 1163-1175
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 78, No. 3 ( 2010-03), p. 1163-1175
    Abstract: Yersinia pestis , the causative agent of plague, autoaggregates within a few minutes of cessation of shaking when grown at 28°C. To identify the autoaggregation factor of Y. pestis , we performed mariner -based transposon mutagenesis. Autoaggregation-defective mutants from three different pools were identified, each with a transposon insertion at a different position within the gene encoding phosphoglucomutase ( pgmA ; y1258 ). Targeted deletion of pgmA in Y. pestis KIM5 also resulted in loss of autoaggregation. Given the previously defined role for phosphoglucomutase in antimicrobial peptide resistance in other organisms, we tested the KIM5 Δ pgmA mutant for antimicrobial peptide sensitivity. The Δ pgmA mutant displayed 〉 1,000-fold increased sensitivity to polymyxin B compared to the parental Y. pestis strain, KIM5. This sensitivity is not due to changes in lipopolysaccharide (LPS) since the LPSs from both Y. pestis KIM5 and the Δ pgmA mutant are identical based on a comparison of their structures by mass spectrometry (MS), tandem MS, and nuclear magnetic resonance analyses. Furthermore, the ability of polymyxin B to neutralize LPS toxicity was identical for LPS purified from both KIM5 and the Δ pgmA mutant. Our results indicate that increased polymyxin B sensitivity of the Δ pgmA mutant is due to changes in surface structures other than LPS. Experiments with mice via the intravenous and intranasal routes did not demonstrate any virulence defect for the Δ pgmA mutant, nor was flea colonization or blockage affected. Our findings suggest that the activity of PgmA results in modification and/or elaboration of a surface component of Y. pestis responsible for autoaggregation and polymyxin B resistance.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00997-09
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2010
    detail.hit.zdb_id: 1483247-1
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