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Berlin Brandenburg

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  • 1
    Language: English
    In: Journal of Bacteriology, 2011, Vol. 193(23), p.6712
    Description: Hopanoids are pentacyclic triterpenoids that are thought to be bacterial surrogates for eukaryotic sterols, such as cholesterol, acting to stabilize membranes and to regulate their fluidity and permeability. To date, very few studies have evaluated the role of hopanoids in bacterial physiology. The synthesis of hopanoids depends on the enzyme squalene-hopene cyclase (Shc), which converts the linear squalene into the basic hopene structure. Deletion of the 2 genes encoding Shc enzymes in Burkholderia cenocepacia K56-2, BCAM2831 and BCAS0167, resulted in a strain that was unable to produce hopanoids, as demonstrated by gas chromatography and mass spectrometry. Complementation of the [DELTA]shc mutant with only BCAM2831 was sufficient to restore hopanoid production to wild-type levels, while introducing a copy of BCAS0167 alone into the [DELTA]shc mutant produced only very small amounts of the hopanoid peak. The [DELTA]shc mutant grew as well as the wild type in medium buffered to pH 7 and demonstrated no defect in its ability to survive and replicate within macrophages, despite transmission electron microscopy (TEM) revealing defects in the organization of the cell envelope. The [DELTA]shc mutant displayed increased sensitivity to low pH, detergent, and various antibiotics, including polymyxin B and erythromycin. Loss of hopanoid production also resulted in severe defects in both swimming and swarming motility. This suggests that hopanoid production plays an important role in the physiology of B. cenocepacia. doi: 10.1128/JB.05979-11
    Keywords: Burkholderia -- Genetic Aspects ; Burkholderia -- Physiological Aspects ; Burkholderia -- Research ; Terpenes -- Physiological Aspects ; Terpenes -- Research ; Microbial Drug Resistance -- Research ; Bacterial Motility -- Physiological Aspects ; Bacterial Motility -- Research;
    ISSN: 1098-5530
    ISSN: 10985530
    ISSN: 00219193
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  • 2
    In: The Journal of Bacteriology, 2011, Vol. 193(15), p.3710
    Description: The O-antigen component of the lipopolysaccharide (LPS) represents a population of polysaccharide molecules with nonrandom (modal) chain length distribution. The number of the repeat O units in each individual O-antigen polymer depends on the Wzz chain length regulator, an inner membrane protein belonging to the polysaccharide copolymerase (PCP) family. Different Wzz proteins confer vastly different ranges of modal lengths (4 to 〉 100 repeat units), despite having remarkably conserved structural folds. The molecular mechanism responsible for the selective preference for a certain number of O units is unknown. Guided by the three-dimensional structures of PCPs, we constructed a panel of chimeric molecules containing parts of two closely related Wzz proteins from Salmonella enterica and Shigella flexneri which confer different O-antigen chain length distributions. Analysis of the O-antigen length distribution imparted by each chimera revealed the region spanning amino acids 67 to 95 (region 67 to 95), region 200 to 255, and region 269 to 274 as primarily affecting the length distribution. We also showed that there is no synergy between these regions. In particular, region 269 to 274 also influenced chain length distribution mediated by two distantly related PCPs, WzzB and FepE. Furthermore, from the 3 regions uncovered in this study, region 269 to 274 appeared to be critical for the stability of the oligomeric form of Wzz, as determined by cross-linking experiments. Together, our data suggest that chain length determination depends on regions that likely contribute to stabilize a supramolecular complex. doi:10.1128/JB.00059-11
    Keywords: Bacterial Proteins -- Research ; Protein Structure -- Research ; O Antigens -- Research ; Lipopolysaccharides -- Research ; Microbial Polysaccharides -- Research;
    ISSN: 0021-9193
    ISSN: 00219193
    E-ISSN: 10985530
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  • 3
    In: Canadian Journal of Microbiology, 2015, Vol.61(9), pp.607-615
    Description: Burkholderia cepacia complex (Bcc) species are a group of Gram-negative opportunistic pathogens that infect the airways of cystic fibrosis patients, and occasionally they infect other immunocompromised patients. Bcc bacteria display high-level multidrug resistance and chronically persist in the infected host while eliciting robust inflammatory responses. Studies using macrophages, neutrophils, and dendritic cells, combined with advances in the genetic manipulation of these bacteria, have increased our understanding of the molecular mechanisms of virulence in these pathogens and the molecular details of cell-host responses triggering inflammation. This article discusses our current view of the intracellular survival of Burkholderia cenocepacia within macrophages.
    Description: Le complexe des espèces de Burkholderia cepacia (Bcc) est un groupe de pathogènes opportunistes à Gram négatif qui infectent les voies respiratoires de patients atteints de fibrose kystique et touchent occasionnellement des patients immunocompromis. Les bactéries Bcc présentent un degré élevé de multirésistance et persistent de manière chronique dans l’hôte infecté tout en provoquant une réponse inflammatoire vigoureuse. Des études employant des macrophages, des neutrophiles et des cellules dendritiques, appuyées par des avancées dans la manipulation génétique de ces bactéries, ont permis de parfaire nos connaissances concernant les mécanismes moléculaires de virulence opérant chez ces pathogènes ainsi que les rouages moléculaires des réponses pro-inflammatoires de la cellule-hôte. Le présent article aborde notre conception actuelle de la survie intracellulaire de Burkholderia cenocepacia dans les macrophages. [Traduit par la Rédaction]
    Keywords: Phagocytosis ; Phagosome ; Cystic Fibrosis ; Autophagy ; Inflammasome ; Cystic Fibrosis Transmembrane Conductance Regulator ; Pyrin ; Cepacia Syndrome ; Macrophage ; Neutrophils ; Amoebae ; Phagocytose ; Phagosome ; Fibrose Kystique ; Autophagie ; Inflammasome ; Régulateur De Conductance Transmembranaire ; Pyrine ; Syndrome De Cepacia ; Macrophage ; Neutrophiles ; Amibes
    ISSN: 0008-4166
    E-ISSN: 1480-3275
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  • 4
    Language: English
    In: Infection and Immunity, 2010, Vol. 78(10), p.4088
    Description: The Burkholderia cepacia complex (Bcc) is a group of genetically related environmental bacteria that can cause chronic opportunistic infections in patients with cystic fibrosis (CF) and other underlying diseases. These infections are difficult to treat due to the inherent resistance of the bacteria to antibiotics. Bacteria can spread between CF patients through social contact and sometimes cause cepacia syndrome, a fatal pneumonia accompanied by septicemia. Burkholderia cenocepacia has been the focus of attention because initially it was the most common Bcc species isolated from patients with CF in North America and Europe. Today, B. cenocepacia, along with Burkholderia multivorans, is the most prevalent Bcc species in patients with CF. Given the progress that has been made in our understanding of B. cenocepacia over the past decade, we thought that it was an appropriate time to review our knowledge of the pathogenesis of B. cenocepacia, paying particular attention to the characterization of virulence determinants and the new tools that have been developed to study them. A common theme emerging from these studies is that B. cenocepacia establishes chronic infections in immunocompromised patients, which depend more on determinants mediating host niche adaptation than those involved directly in host cells and tissue damage.
    Keywords: Burkholderia Infections -- Microbiology ; Burkholderia Cepacia Complex -- Pathogenicity;
    ISSN: 0019-9567
    ISSN: 00199567
    E-ISSN: 10985522
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  • 5
    Language: English
    In: The Journal of biological chemistry, 12 November 2010, Vol.285(46), pp.35988-98
    Description: The type VI secretion system (T6SS) contributes to the virulence of Burkholderia cenocepacia, an opportunistic pathogen causing serious chronic infections in patients with cystic fibrosis. BcsK(C) is a highly conserved protein among the T6SSs in Gram-negative bacteria. Here, we show that BcsK(C) is required for Hcp secretion and cytoskeletal redistribution in macrophages upon bacterial infection. These two phenotypes are associated with a functional T6SS in B. cenocepacia. Experiments employing a bacterial two-hybrid system and pulldown assays demonstrated that BcsK(C) interacts with BcsL(B), another conserved T6SS component. Internal deletions within BcsK(C) revealed that its N-terminal domain is necessary and sufficient for interaction with BcsL(B). Fractionation experiments showed that BcsK(C) can be in the cytosol or tightly associated with the outer membrane and that BcsK(C) and BcsL(B) form a high molecular weight complex anchored to the outer membrane that requires BcsF(H) (a ClpV homolog) to be assembled. Together, our data show that BcsK(C)/BcsL(B) interaction is essential for the T6SS activity in B. cenocepacia.
    Keywords: Bacterial Proteins -- Metabolism ; Burkholderia Cenocepacia -- Metabolism ; Cell Membrane -- Metabolism ; Multiprotein Complexes -- Metabolism
    ISSN: 00219258
    E-ISSN: 1083-351X
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  • 6
    Language: English
    In: PLoS ONE, 01 January 2013, Vol.8(7), p.e68874
    Description: The overall antibiotic resistance of a bacterial population results from the combination of a wide range of susceptibilities displayed by subsets of bacterial cells. Bacterial heteroresistance to antibiotics has been documented for several opportunistic Gram-negative bacteria, but the mechanism of heteroresistance is unclear. We use Burkholderia cenocepacia as a model opportunistic bacterium to investigate the implications of heterogeneity in the response to the antimicrobial peptide polymyxin B (PmB) and also other bactericidal antibiotics. Here, we report that B. cenocepacia is heteroresistant to PmB. Population analysis profiling also identified B. cenocepacia subpopulations arising from a seemingly homogenous culture that are resistant to higher levels of polymyxin B than the rest of the cells in the culture, and can protect the more sensitive cells from killing, as well as sensitive bacteria from other species, such as Pseudomonas aeruginosa and Escherichia coli. Communication of resistance depended on upregulation of putrescine synthesis and YceI, a widely conserved low-molecular weight secreted protein. Deletion of genes for the synthesis of putrescine and YceI abrogate protection, while pharmacologic inhibition of putrescine synthesis reduced resistance to polymyxin B. Polyamines and YceI were also required for heteroresistance of B. cenocepacia to various bactericidal antibiotics. We propose that putrescine and YceI resemble "danger" infochemicals whose increased production by a bacterial subpopulation, becoming more resistant to bactericidal antibiotics, communicates higher level of resistance to more sensitive members of the population of the same or different species.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 7
    In: PLoS ONE, 2013, Vol.8(7)
    Description: The C-type lectin RegIIIβ can kill certain Gram-positive and Gram-negative bacteria. The susceptibility of S . Typhimurium depends on the bacterial growth phase, i.e., bacteria from the logarithmic growth phase do bind RegIIIβ and are subsequently killed. Lipid A is one of the bacterial targets for RegIIIβ. However, at the molecular level, it is not understood how RegIIIβ interacts with and kills Gram-negative bacteria. Here, we show that RegIIIβ interacts with Gram-negative bacteria in two distinct steps. Initially, it binds to surface-exposed lipid A. The lipid A can be shielded by the O-antigen of lipopolysaccharide (LPS), as indicated by the exquisite susceptibility of wbaP mutants to RegIIIβ-mediated killing. Increased cell viability after incubation with an anti-lipid A antibody also supports this conclusion. This RegIIIβ-binding permeabilizes the outer membrane to hydrophobic dyes like Ethidium bromide or to bulky bacteriolytic enzymes like lysozyme. Conversely, compromising the outer membrane integrity by the mild detergent Triton X-100 enhances the antibacterial effect of RegIIIβ. Based on our observations, we conclude that RegIIIβ interacts with Gram-negative bacteria in two subsequent steps. Initially, it binds to the outer membrane thus leading to outer membrane permeabilization. This initial step is necessary for RegIIIβ to reach a second, still not well understood target site (presumably localized in the periplasm or the cytoplasmic membrane), thereby triggering bacterial death. This provides novel insights into the outer membrane-step of the bactericidal mechanism of RegIIIβ.
    Keywords: Research Article ; Biology ; Medicine
    E-ISSN: 1932-6203
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  • 8
    Language: English
    In: Journal of Bacteriology, May, 2012, Vol.194(9-10), p.2646(12)
    Description: Escherichia coli K-12 WcaJ and the Caulobacter crescentus HfsE, PssY, and PssZ enzymes are predicted to initiate the synthesis of colanic acid (CA) capsule and holdfast polysaccharide, respectively. These proteins belong to a prokaryotic family of membrane enzymes that catalyze the formation of a phosphoanhydride bond joining a hexose-1-phosphate with undecaprenyl phosphate (Und-P). In this study, in vivo complementation assays of an E. coli K-12 wcaJ mutant demonstrated that WcaJ and PssY can complement CA synthesis. Furthermore, WcaJ can restore holdfast production in C. crescentus. In vitro transferase assays demonstrated that both WcaJ and PssY utilize UDP-glucose but not UDP-galactose. However, in a strain of Salmonella enterica serovar Typhimurium deficient in the WbaP O antigen initiating galactosyltransferase, complementation with WcaJ or PssY resulted in O-antigen production. Gas chromatography-mass spectrometry (GC-MS) analysis of the lipopolysaccharide (LPS) revealed the attachment of both CA and O-antigen molecules to lipid A-core oligosaccharide (OS). Therefore, while UDP-glucose is the preferred substrate of WcaJ and PssY, these enzymes can also utilize UDP-galactose. This unexpected feature of WcaJ and PssY may help to map specific residues responsible for the nucleotide diphosphate specificity of these or similar enzymes. Also, the reconstitution of O-antigen synthesis in Salmonella, CA capsule synthesis in E. coli, and holdfast synthesis provide biological assays of high sensitivity to examine the sugar-1-phosphate transferase specificity of heterologous proteins.
    Keywords: Escherichia Coli -- Genetic Aspects ; Caulobacter -- Genetic Aspects ; Microbiological Synthesis -- Research ; Gas Chromatography -- Usage ; Glycosyltransferases -- Research
    ISSN: 0021-9193
    Source: Cengage Learning, Inc.
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  • 9
    Language: English
    In: Applied and environmental microbiology, 01 February 2016, Vol.82(3), pp.843-56
    Description: Burkholderia cenocepacia, a member of the B. cepacia complex (Bcc), is an opportunistic pathogen causing serious chronic infections in patients with cystic fibrosis. Tyrosine phosphorylation has emerged as an important posttranslational modification modulating the physiology and pathogenicity of Bcc bacteria. Here, we investigated the predicted bacterial tyrosine kinases BCAM1331 and BceF and the low-molecular-weight protein tyrosine phosphatases BCAM0208, BceD, and BCAL2200 of B. cenocepacia K56-2. We show that BCAM1331, BceF, BCAM0208, and BceD contribute to biofilm formation, while BCAL2200 is required for growth under nutrient-limited conditions. Multiple deletions of either tyrosine kinase or low-molecular-weight protein tyrosine phosphatase genes resulted in the attenuation of B. cenocepacia intramacrophage survival and reduced pathogenicity in the Galleria mellonella larval infection model. Experimental evidence indicates that BCAM1331 displays reduced tyrosine autophosphorylation activity compared to that of BceF. With the artificial substrate p-nitrophenyl phosphate, the phosphatase activities of the three low-molecular-weight protein tyrosine phosphatases demonstrated similar kinetic parameters. However, only BCAM0208 and BceD could dephosphorylate BceF. Further, BCAL2200 became tyrosine phosphorylated in vivo and catalyzed its autodephosphorylation. Together, our data suggest that despite having similar biochemical activities, low-molecular-weight protein tyrosine phosphatases and tyrosine kinases have both overlapping and specific roles in the physiology of B. cenocepacia.
    Keywords: Biofilms -- Growth & Development ; Burkholderia Cenocepacia -- Physiology ; Protein Tyrosine Phosphatases -- Metabolism ; Protein-Tyrosine Kinases -- Metabolism
    ISSN: 00992240
    E-ISSN: 1098-5336
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  • 10
    Language: English
    In: Applied and Environmental Microbiology, Feb 1, 2016, Vol.82(3), pp.843-856
    Description: The article describes the investigation of the predicted bacterial tyrosine kinases BCAM1331 and BceF and the low-molecular-weight protein tyrosine phosphatases BCAM0208, BceD, and BCAL2200 of Burkholderia cenocepacia K56-2. It is shown that BCAM1331, BceF, BCAM0208, and BceD contribute to biofilm formation, while BCAL2200 is needed for growth under nutrient-limited conditions. Moreover, BCAM1331 shows reduced tyrosine autophosphorylation activity compared to that of BceF, and only BCAM0208 and BceD can dephosphorylate BceF.
    Keywords: Burkholderia Cepacia – Genetic Aspects ; Burkholderia Cepacia – Research ; Microbial Mats – Research ; Tyrosine – Research
    ISSN: 0099-2240
    Source: Cengage Learning, Inc.
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