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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Neisseria meningitidis (Nm) isolates from disease or during carriage express, on their outer membranes, one or more of a family of closely related proteins designated Opa proteins. In this study, we have examined the potential rotes of Nm Opa proteins in bacterial attachment and invasion of endothelial as well as epithelial cells and compared the influence of Opa proteins with that of Ope protein, which has been previously shown to increase bacterial interactions with eukaryotic cells. Several variants expressing different Opa proteins (A, B, D) or Opc were selected from a culture of capsule-deficient non-piliated bacteria of strain C751. Although the Opa proteins increased bacterial attachment and invasion of endothelial cells, Opc was the most effective protein in increasing bacterial interactions with these cells. In contrast, attachment to several human epithelial cells was facilitated at least as much by OpaB as Opc protein. OpaA was largely without effect whereas OpaD conferred intermediate attachment. OpaB also increased invasion of epithelial cells; more bacteria were internalized by Chang conjunctival cells compared with Hep-2 larynx carcinoma or A549 lung carcinoma cells. Monoclonal antibody reacting with OpaB inhibited bacterial interactions with the host cells. Opa-mediated interactions were also eliminated or significantly reduced in variants expressing capsule or those with sialylated lipopolysaccharide. These data are consistent with the notion that environmental factors controlling capsule and lipopolysaccharide phenotype may modulate bacterial interactions mediated by these OM proteins. In permissive microenvironments, some Opa proteins may be important in bacterial colonization and translocation in addition to Opc. The data also support the notion that Nm Opa may confer tissue tropism.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 36 (2000), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Natural sequence variation was investigated among serogroup A subgroup IV-1 Neisseria meningitidis isolated from diseased patients and healthy carriers in The Gambia, West Africa. The frequencies of DNA import were analysed by sequencing fragments of four linked genes encoding the immunogenic outer membrane proteins TbpB (transferrin binding protein B) and OpaA (an adhesin) plus two housekeeping enzymes. Seventeen foreign tbpB alleles were independently imported into the 98 strains tested, apparently due to immune selection. The median size of the imported DNA fragments was 5 kb, resulting in the occasional concurrent import of linked housekeeping genes by hitchhiking. Sequences of tbpB from other strains of N. meningitidis as well as commensal Neisseria lactamica and Neisseria spp. isolated from the same geographical area revealed that these species share a common tbpB gene pool and identified several examples of interspecific genetic exchange. These observations indicate that recombination can be more frequent between related species than within a species and indicate that effective vaccination against serogroup B meningococcal disease may be difficult to achieve.
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Serogroup A meningococci of subgroups III, IV-1 and IV-2 are probably descended from a common ancestor that existed in the nineteenth century. The 10.5 kb sequences spanning five distinct chromosomal loci, encoding cell-surface antigens, a secreted protease or housekeeping genes and intergenic regions, were almost identical in strains of those subgroups isolated in 1966, 1966 and 1917 respectively. During the subsequent two to three decades, all of these loci varied as a result of mutation, translocation or import of DNA from unrelated neisseriae. Thus, microevolution occurs frequently in naturally transformable bacteria. Many variants were isolated only once or within a single geographical location and disappeared thereafter. Other variants achieved genetic fixation within months or a few years. The speed with which sequence variation is either eliminated or fixed may reflect sequential bottlenecks associated with epidemic spread and contrasts with the results of phylogenetic analyses from bacteria that do not cause epidemics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Capsular polysaccharides of serogroup C, W-135 and Y meningococci were previously reported to be O-acetylated at the sialic acid residues. There is evidence that O-acetylation affects the immunogenicity of polysaccharide vaccines. We identified genes indispensable for O-acetylation of serogroup C, W-135 and Y meningococci downstream of the capsule synthesis genes siaA–D. The genes were co-transcribed with the sia operon as shown by reverse transcription polymerase chain reaction analysis. The putative capsular polysaccharide O-acetyltransferases were designated OatC and OatWY. The protein OatWY of serogroups W-135 and Y showed sequence homologies to members of the NodL–LacA–CysE family of bacterial acetyltransferases, whereas no sequence homology with any known protein in the different databases was found for the serogroup C protein OatC. In serogroup W-135 and Y meningococci, several clonal lineages either lacked OatWY or OatWY was inactivated by insertion of IS1301. For serogroup C meningococci, we observed in vitro phase variation of O-acetylation, which resulted from slipped-strand mispairing in homopolymeric tracts. This finding explains the observation of naturally occurring de-O-acetylated serogroup C meningococci. Our report is the first description of sequences of sialic acid O-acetyltransferase genes that have not been cloned from either other bacterial or mammalian organisms.
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Infection of the stomach by Helicobacter pylori is ubiquitous among humans. However, although H. pylori strains from different geographic areas are associated with clear phylogeographic differentiation, the age of an association between these bacteria with humans remains highly controversial. ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 257 (1975), S. 652-656 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The operon structure of the tra cistrons on the F sex factor has been investigated using Mu-1 bacteriophage. Twelve tra cistrons comprise one polycistronic operon 15×106 to 20×106 daltons ...
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  • 7
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Opa proteins of Neisseria meningitidis exhibit translational phase variation via addition or deletion of repetitive coding repeat units within the DNA encoding the protein leader sequence. In contrast, Opc phase variation is the result of transcriptional regulation. Transcription starts 13 nucleotides after the -10 region of an unusual promoter sequence containing a variable number of contiguous cytidine residues and lacking a - 35 region. Efficient expression of Opc occurred in strains with 12 to 13 cytidine residues, intermediate expression in strains with 11 or 14 residues and no expression with ≤ 10 or ≥ 15 residues. This unusual regulation may have evolved because the Opc protein enables meningococcal invasion and is immunogenic.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 23 (1997), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A two-dimensional structural model was devised for the Opc outer membrane protein invasin which contains 10 transmembrane strands and five surface-exposed loops. One continuous epitope recognized by three monoclonal antibodies was localized to the tip of loop 2 by synthetic peptides and site-directed mutagenesis while a second, discontinuous epitope recognized by a fourth antibody was localized to loops 4 and 5 by insertion mutagenesis. These monoclonal antibodies are bactericidal and inhibit adhesion and invasion. Most of the T-cell epitopes defined by Wiertz et al. (1996) were localized to the transmembrane strands. Oligonucleotides encoding a foreign epitope (∇) from Semliki Forest virus were inserted into BglII restriction sites created by site-directed mutagenesis. The ∇ epitopes inserted in all five predicted loops were recognized on the cell surface of live Escherichia coli bacteria by a monoclonal antibody and are exposed while ∇ epitopes in the N-terminus or three predicted turns were not. The results thus confirm important predictions of the model and define five permissive sites within surface-exposed loops which can be used to insert foreign epitopes.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 21 (1996), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 11 (1994), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Extensive epidemiological analyses of epidemics of meningococcal meningitis have resulted in large, well-defined strain collections which represent the local diversity and global spread of serogroup A bacteria. Several genes for cell surface proteins are conserved during spread, with a few exceptions: analysis of these exceptions has revealed some of the phenomena which can lead to microevolution. Micro-evolution is so rapid with serogroup A meningococcal that several independent recombination events have been documented within the last few decades. In a few cases, the recombinant bacteria have become established by clonal replacement plus epidemic spread. Comparison with other bacteria indicates that serogroup A meningococcal provide a number of advantages for analysis of microevolution.
    Type of Medium: Electronic Resource
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