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  • 2000-2004  (3)
  • 2004  (3)
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  • 2000-2004  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 58 (2004), S. 365-390 
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: The genus Bartonella comprises several important human pathogens that cause a wide range of clinical manifestations: cat-scratch disease, trench fever, Carrion's disease, bacteremia with fever, bacillary angiomatosis and peliosis, endocarditis, and neuroretinitis. Common features of bartonellae include transmission by blood-sucking arthropods and the specific interaction with endothelial cells and erythrocytes of their mammalian hosts. For each Bartonella species, the invasion and persistent intracellular colonization of erythrocytes are limited to a specific human or animal reservoir host. In contrast, endothelial cells are target host cells in probably all mammals, including humans. Bartonellae subvert multiple cellular functions of human endothelial cells, resulting in cell invasion, proinflammatory activation, suppression of apoptosis, and stimulation of proliferation, which may cumulate in vasoproliferative tumor growth. This review summarizes our understanding of Bartonella-host cell interactions and the molecular mechanisms of bacterial virulence and persistence. In addition, current controversies and unanswered questions in this area are highlighted.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bartonella henselae is an arthropod-borne zoonotic pathogen causing intraerythrocytic bacteraemia in the feline reservoir host and a broad range of clinical manifestations in incidentally infected humans. Remarkably, B. henselae can specifically colonize the human vascular endothelium, resulting in inflammation and the formation of vasoproliferative lesions known as bacillary angiomatosis and bacillary peliosis. Cultured human endothelial cells provide an in vitro system to study this intimate interaction of B. henselae with the vascular endothelium. However, little is known about the bacterial virulence factors required for this pathogenic process. Recently, we identified the type IV secretion system (T4SS) VirB as an essential pathogenicity factor in Bartonella, required  to  establish  intraerythrocytic  infection  in the mammalian reservoir. Here, we demonstrate that the VirB T4SS also mediates most of the virulence attributes associated  with  the  interaction  of B. henselae during the interaction with human endothelial cells. These include: (i) massive rearrangements of the actin cytoskeleton, resulting in the formation of bacterial aggregates and their internalization by the invasome structure; (ii) nuclear factor κB-dependent proinflammatory activation, leading to cell adhesion molecule expression and chemokine secretion, and (iii) inhibition of apoptotic cell death, resulting in enhanced endothelial cell survival. Moreover, we show that the VirB system mediates cytostatic and cytotoxic effects at high bacterial titres, which interfere with a potent VirB-independent mitogenic activity. We conclude that the VirB T4SS is a major virulence determinant of B. henselae, required for targeting multiple endothelial cell functions exploited by this vasculotropic pathogen.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Summary The flagellar system of Helicobacter pylori, which comprises more than 40 mostly unclustered genes, is essential for colonization of the human stomach mucosa. In order to elucidate the complex transcriptional circuitry of flagellar biosynthesis in H. pylori and its link to other cell functions, mutants in regulatory genes governing flagellar biosynthesis (rpoN, flgR, flhA, flhF, HP0244) and whole-genome microarray technology were used in this study. The regulon controlled by RpoN, its activator FlgR (FleR) and the cognate histidine kinase HP0244 (FleS) was characterized on a genome-wide scale for the first time. Seven novel genes (HP1076, HP1233, HP1154/1155, HP0366/367, HP0869) were identified as belonging to RpoN-associated flagellar regulons. The hydrogenase accessory gene HP0869 was the only annotated non-flagellar gene in the RpoN regulon. Flagellar basal body components FlhA and FlhF were characterized as functional equivalents to master regulators in H. pylori, as their absence led to a general reduction of transcripts in the RpoN (class 2) and FliA (class 3) regulons, and of 24 genes newly attributed to intermediate regulons, under the control of two or more promoters. FlhA- and FlhF-dependent regulons comprised flagellar and non-flagellar genes. Transcriptome analysis revealed that negative feedback regulation of the FliA regulon was dependent on the antisigma factor FlgM. FlgM was also involved in FlhA- but not FlhF-dependent feedback control of the RpoN regulon. In contrast to other bacteria, chemotaxis and flagellar motor genes were not controlled by FliA or RpoN. A true master regulator of flagellar biosynthesis is absent in H. pylori, consistent with the essential role of flagellar motility and chemotaxis for this organism.
    Type of Medium: Electronic Resource
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