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Berlin Brandenburg

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  • 1
    Language: English
    In: Journal of molecular biology, 23 July 2010, Vol.400(4), pp.682-8
    Description: OmpT, an outer membrane porin of Vibrio cholerae, is tightly regulated by the organism in response to different environments. Two transcriptional regulators, cAMP receptor protein (CRP) and ToxR, compete at the ompT promoter region. CRP activates ompT transcription by a loop-forming mechanism, while ToxR functions as an antiactivator and repressor, depending on its interplay with CRP. VrrA, a 140-nt small noncoding RNA in V. cholerae, is controlled by the alternative sigma factor sigma(E). We have demonstrated previously that VrrA represses ompA translation by base-pairing with the 5' region of the mRNA, thereby affecting the release of outer membrane vesicles and modulating the colonization ability of V. cholerae. In this study, we demonstrate that VrrA RNA represses ompT translation by base-pairing with the 5' region of the mRNA and that regulation requires the RNA chaperone protein Hfq. These results add new insight into the regulation of OmpT. In addition to pH/temperature signals via the ToxR regulon and carbon source signals via the cAMP-CRP complex, OmpT is further regulated by signals received via the sigma(E) regulon through VrrA.
    Keywords: Gene Expression Regulation, Bacterial ; Bacterial Proteins -- Biosynthesis ; Host Factor 1 Protein -- Metabolism ; Porins -- Biosynthesis ; RNA, Bacterial -- Metabolism ; RNA, Untranslated -- Metabolism ; Vibrio Cholerae -- Physiology
    ISSN: 00222836
    E-ISSN: 1089-8638
    E-ISSN: 20462069
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  • 2
    Language: English
    In: Journal of Biological Chemistry, 2011, Vol.286(14), pp.12389-12396
    Description: Gram-negative bacteria can alter the composition of the Lipopolysaccharide (LPS) layer of the outer membrane as a response to different growth conditions and external stimuli. These alterations can, for example, promote attachment to surfaces and biofilm...
    Keywords: Medical And Health Sciences ; Medical Biotechnology ; Medical Biotechnology (With A Focus On Cell Biology (Including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry Or Biopharmacy) ; Medicin Och Hälsovetenskap ; Medicinsk Bioteknologi ; Medicinsk Bioteknologi (Med Inriktning Mot Cellbiologi (Inklusive Stamcellsbiologi), Molekylärbiologi, Mikrobiologi, Biokemi Eller Biofarmaci) ; Bacteria ; Carbohydrate ; Cell Surface ; Cell Wall ; Lipid ; Peptides ; Spectroscopy ; Chemical Composition ; Multivariate Analysis ; X-Ray Photoelectron Spectroscopy
    ISSN: 0021-9258
    E-ISSN: 1083351X
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  • 3
    In: Nature, 2013, Vol.496(7446), p.508
    Description: Membranes allow the compartmentalization of biochemical processes and are therefore fundamental to life. The conservation of the cellular membrane, combined with its accessibility to secreted proteins, has made it a common target of factors mediating antagonistic interactions between diverse organisms. Here we report the discovery of a diverse superfamily of bacterial phospholipase enzymes. Within this superfamily, we defined enzymes with phospholipase A1 (PLA 1 ) and A2 (PLA 2 ) activity, which are common in host cell-targeting bacterial toxins and the venoms of certain insects and reptiles 1 , 2 . However, we find that the fundamental role of the superfamily is to mediate antagonistic bacterial interactions as effectors of the type VI secretion system (T6SS) translocation apparatus; accordingly, we name these proteins type VI lipase effectors (Tle). Our analyses indicate that PldA of Pseudomonas aeruginosa , a eukaryotic-like phospholipase D (PLD) 3 , is a member of the Tle superfamily and the founding substrate of the haemolysin co-regulated protein secretion island II T6SS (H2-T6SS). While prior studies have specifically implicated PldA and the H2-T6SS in pathogenesis 3 – 5 , we uncovered a specific role for the effector and its secretory machinery in intra- and inter-species bacterial interactions. Furthermore we find that this effector achieves its antibacterial activity by degrading phosphatidylethanolamine (PE), the major component of bacterial membranes. The surprising finding that virulence-associated phospholipases can serve as specific antibacterial effectors suggests that interbacterial interactions are a relevant factor driving the ongoing evolution of pathogenesis.
    Keywords: Article;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 4
    In: Molecular Microbiology, January 2014, Vol.91(2), pp.326-347
    Description: In , 41 chitin‐inducible genes, including the genes involved in natural competence for uptake, are governed by the orphan two‐component system () sensor kinase . However, the mechanism by which controls the expression of these genes is currently unknown. Here, we report the involvement of a novel transcription factor termed ‘’ in this process. is a transmembrane protein that contains a large periplasmic domain and a cytoplasmic ‐type ‐binding domain, but lacks signature domains. Inactivation of abolished natural competence as well as transcription of the gene encoding a chitin‐induced small essential for competence gene expression. A fragment containing the ‐binding domain specifically bound to and activated transcription from the promoter. Intracellular levels were unaffected by disruption of and coexpression of and in recovered transcription of the chromosomally integrated :: gene, suggesting that is post‐translationally modulated by during transcriptional activation; however, this regulation persisted when the canonical phosphorelay residues of were mutated. The results presented here suggest that operates a chitin‐induced non‐canonical signal transduction cascade through , leading to transcriptional activation of .
    Keywords: Transcription (Genetics) ; Cholera Toxin ; Orphans ; Genes ; Rna;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 5
    Language: English
    In: PLoS ONE, 2013, Vol. 8(1)
    Description: Staphylococcus aureus causes a wide spectrum of infections in humans, ranging from superficial cutaneous infections, infections in the circum-oral region, to life-threatening bacteremia. It was recently demonstrated that Gram-positive organisms such as S. aureus liberate membrane-derived vesicles (MVs), which analogously to outer membrane vesicles (OMVs) of Gram-negative bacteria can play a role in delivering virulence factors to host cells. In the present study we have shown that cholesterol-dependent fusion of S. aureus MVs with the plasma membrane represents a route for delivery of a key virulence factor, α-toxin (α-hemolysin; Hla) to human cells. Most S. aureus strains produce this 33-kDa pore-forming protein, which can lyse a wide range of human cells, and induce apoptosis in T-lymphocytes. Our results revealed a tight association of biologically active α-toxin with membrane-derived vesicles isolated from S. aureus strain 8325-4. Concomitantly, α-toxin contributed to HeLa cell cytotoxicity of MVs, and was the main vesicle-associated protein responsible for erythrocyte lysis. In contrast, MVs obtained from an isogenic hla mutant were significantly attenuated with regards to both causing lysis of erythrocytes and death of HeLa cells. This is to our knowledge the first recognition of an S. aureus MV-associated factor contributing to host cell cytotoxicity.
    Keywords: Medical And Health Sciences ; Clinical Medicine ; Dentistry ; Medicin Och Hälsovetenskap ; Klinisk Medicin ; Odontologi
    ISSN: 1932-6203
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  • 6
    Language: English
    In: Infection and Immunity, 2014, Vol. 82(10), pp. 4034-4046
    Description: Aggregatibacter actinomycetemcomitans is an oral and systemic pathogen associated with aggressive forms of periodontitis, and endocarditis. We recently demonstrated that OMVs disseminated by A. actinomycetemcomitans could deliver multiple proteins including biologically active cytolethal distending toxin (CDT) into the cytosol of HeLa cells and human gingival fibroblasts (HGF). In the present work we have used immunoelectron- and confocal microscopy analysis, and fluorescently labeled vesicles to further investigate mechanisms for A. actinomycetemcomitans OMV-mediated delivery of bacterial antigens to these host cells. Our results supported that OMVs were internalized into the perinuclear region of HeLa cells and HGF. Co-localization analysis revealed that internalized OMVs co-localized with the endoplasmic reticulum, and carried antigens, detected using an antibody specific to whole A. actinomycetemcomitans serotype a cells. Consistent with OMV internalization mediating intracellular antigen exposure, the vesicles acted as strong inducers of cytoplasmic peptidoglycan sensor NOD1- and NOD2-dependent NF-κB activation in human embryonic kidney cells. Moreover, NOD1 was the main sensor of OMV-delivered peptidoglycan in myeloid THP1 cells, contributing to the overall inflammatory responses induced by the vesicles. This work reveals a role of A. actinomycetemcomitans OMVs as a trigger of innate immunity via carriage of NOD1- and NOD2-active PAMPs.
    Keywords: Medical And Health Sciences ; Clinical Medicine ; Dentistry ; Medicin Och Hälsovetenskap ; Klinisk Medicin ; Odontologi ; Natural Sciences ; Biological Sciences ; Microbiology ; Naturvetenskap ; Biologiska Vetenskaper ; Mikrobiologi
    ISSN: 0019-9567
    E-ISSN: 10985522
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  • 7
    Language: English
    In: PLoS ONE, 2012, Vol. 7(12), p. e51241
    Description: Lipopolysaccharide (LPS) is the major component of the surface of Gram-negative bacteria and its polysaccharide portion is situated at the outermost region. We investigated the relationship between the polysaccharide portion of LPS and biofilm formation using a series of Escherichia coli mutants defective in genes earlier shown to affect the LPS sugar compositions. Biofilm formation by a deep rough LPS mutant, the hldE strain, was strongly enhanced in comparison with the parental strain and other LPS mutants. The hldE strain also showed a phenotype of increased auto-aggregation and stronger cell surface hydrophobicity compared to the wild-type. Similar results were obtained with another deep rough LPS mutant, the waaC strain whose LPS showed same molecular mass as that of the hldE strain. Confocal laser scanning microscopy (CLSM) analysis and biofilm formation assay using DNase I revealed that biofilm formation by the hldE strain was dependent on extracellular DNA. Furthermore, a loss of flagella and an increase in amount of outer membrane vesicles in case of the hldE strain were also observed by transmission electron microscopy and atomic force microscopy, respectively. In addition, we demonstrated that a mutation in the hldE locus, which alters the LPS structure, caused changes in both expression and properties of several surface bacterial factors involved in biofilm formation and virulence. We suggest that the implication of these results should be considered in the context of biofilm formation on abiotic surfaces, which is frequently associated with nosocominal infections such as the catheter-associated infections.
    Keywords: Pseudomonas-Aeruginosa Pao1; O-Antigen Lipopolysaccharide; Negative Antivirulence Drugs; Mouse Large-Intestine; Extracellular Dna; Porphyromonas-Gingivalis; Salmonella-Typhimurium; Klebsiella-Pneumoniae; Monoclonal-Antibody; Membrane-Vesicles ; Medical And Health Sciences ; Basic Medicine ; Cell And Molecular Biology ; Medicin Och Hälsovetenskap ; Medicinska Och Farmaceutiska Grundvetenskaper ; Cell- Och Molekylärbiologi
    ISSN: 1932-6203
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  • 8
    Language: English
    In: PLoS ONE, 2015, Vol. 10(2)
    Description: Clustered regularly interspaced short palindromic repeats (CRISPR) are polymorphic elements found in the genome of some or all strains of particular bacterial species, providing them with a system of acquired immunity against invading bacteriophages and plasmids. Two CRISPR-Cas systems have been identified in Acinetobacter baumannii, an opportunistic pathogen with a remarkable capacity for clonal dissemination. In this study, we investigated the mode of evolution and diversity of spacers of the CRISPR-cas subtype I-Fb locus in a global collection of 76 isolates of A. baumannii obtained from 14 countries and 4 continents. The locus has basically evolved from a common ancestor following two main lineages and several pathways of vertical descent. However, this vertical passage has been interrupted by occasional events of horizontal transfer of the whole locus between distinct isolates. The isolates were assigned into 40 CRISPR-based sequence types (CST). CST1 and CST23-24 comprised 18 and 9 isolates, representing two main sub-clones of international clones CC1 and CC25, respectively. Epidemiological data showed that some of the CST1 isolates were acquired or imported from Iraq, where it has probably been endemic for more than one decade and occasionally been able to spread to USA, Canada, and Europe. CST23-24 has shown a remarkable ability to cause national outbreaks of infections in Sweden, Argentina, UAE, and USA. The three isolates of CST19 were independently imported from Thailand to Sweden and Norway, raising a concern about the prevalence of CST19 in Thailand. Our study highlights the dynamic nature of the CRISPR-cas subtype I-Fb locus in A. baumannii, and demonstrates the possibility of using a CRISPR-based approach for subtyping a significant part of the global population of A. baumannii.
    Keywords: Medical And Health Sciences ; Medical Biotechnology ; Medical Biotechnology (With A Focus On Cell Biology (Including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry Or Biopharmacy) ; Medicin Och Hälsovetenskap ; Medicinsk Bioteknologi ; Medicinsk Bioteknologi (Med Inriktning Mot Cellbiologi (Inklusive Stamcellsbiologi), Molekylärbiologi, Mikrobiologi, Biokemi Eller Biofarmaci)
    ISSN: 1932-6203
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  • 9
    Language: English
    In: PLoS ONE, 2014, Vol. 9(9)
    Description: Background Outer membrane vesicles (OMVs) released from Gram-negative bacteria can serve as vehicles for the translocation of virulence factors. Vibrio cholerae produce OMVs but their putative role in translocation of effectors involved in pathogenesis has not been well elucidated. The V. cholerae cytolysin (VCC), is a pore-forming toxin that lyses target eukaryotic cells by forming transmembrane oligomeric β-barrel channels. It is considered a potent toxin that contributes to V. cholerae pathogenesis. The mechanisms involved in the secretion and delivery of the VCC have not been extensively studied.Methodology/Principal Findings OMVs from V. cholerae strains were isolated and purified using a differential centrifugation procedure and Optiprep centrifugation. The ultrastructure and the contents of OMVs were examined under the electron microscope and by immunoblot analyses respectively. We demonstrated that VCC from V. cholerae strain V:5/04 was secreted in association with OMVs and the release of VCC via OMVs is a common feature among V. cholerae strains. The biological activity of OMV-associated VCC was investigated using contact hemolytic assay and epithelial cell cytotoxicity test. It showed toxic activity on both red blood cells and epithelial cells. Our results indicate that the OMVs architecture might play a role in stability of VCC and thereby can enhance its biological activities in comparison with the free secreted VCC. Furthermore, we tested the role of OMV-associated VCC in host cell autophagy signalling using confocal microscopy and immunoblot analysis. We observed that OMV-associated VCC triggered an autophagy response in the target cell and our findings demonstrated for the first time that autophagy may operate as a cellular defence mechanism against an OMV-associated bacterial virulence factor.Conclusion/Significance Biological assays of OMVs from the V. cholerae strain V:5/04 demonstrated that OMV-associated VCC is indeed biologically active and induces toxicity on mammalian cells and furthermore can induce autophagy.
    Keywords: Medical And Health Sciences ; Medical Biotechnology ; Medical Biotechnology (With A Focus On Cell Biology (Including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry Or Biopharmacy) ; Medicin Och Hälsovetenskap ; Medicinsk Bioteknologi ; Medicinsk Bioteknologi (Med Inriktning Mot Cellbiologi (Inklusive Stamcellsbiologi), Molekylärbiologi, Mikrobiologi, Biokemi Eller Biofarmaci)
    ISSN: 1932-6203
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  • 10
    Language: English
    In: PLoS ONE, 2014, Vol. 9(7)
    Description: Vibrio cholerae biofilms contain exopolysaccharide and three matrix proteins RbmA, RbmC and Bap1. While much is known about exopolysaccharide regulation, little is known about the mechanisms by which the matrix protein components of biofilms are regulated. VrrA is a conserved, 140-nt sRNA of V. cholerae, whose expression is controlled by sigma factor sigma(E). In this study, we demonstrate that VrrA negatively regulates rbmC translation by pairing to the 5' untranslated region of the rbmC transcript and that this regulation is not stringently dependent on the RNA chaperone protein Hfq. These results point to VrrA as a molecular link between the sigma(E)-regulon and biofilm formation in V. cholerae. In addition, VrrA represents the first example of direct regulation of sRNA on biofilm matrix component, by-passing global master regulators.
    Keywords: Medical And Health Sciences ; Basic Medicine ; Cell And Molecular Biology ; Medicin Och Hälsovetenskap ; Medicinska Och Farmaceutiska Grundvetenskaper ; Cell- Och Molekylärbiologi ; Medical And Health Sciences ; Clinical Medicine ; Infectious Medicine ; Medicin Och Hälsovetenskap ; Klinisk Medicin ; Infektionsmedicin ; Medical And Health Sciences ; Basic Medicine ; Microbiology In The Medical Area ; Medicin Och Hälsovetenskap ; Medicinska Och Farmaceutiska Grundvetenskaper ; Mikrobiologi Inom Det Medicinska Området
    ISSN: 1932-6203
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