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  • 1
    Electronic Resource
    Electronic Resource
    Evaluation of cytotoxic activity in fecal filtrates from patients with Campylobacter jejuni or Campylobacter coli enteritis (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 70 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We sought to determine the prevalence of cytotoxic activity in fecal filtrates from persons with C. jejuni or C. coli enteritis. Stool specimens were collected from 20 persons with C. jejuni or C. coli enteritis, 20 persons with acute diarrheal illnesses of other causes, and 9 healthy, asymptomatic persons. Fecal filtrates were then incubated with Chinese hamster ovary (CHO) or HeLa cells. The fecal filtrate from 1 of the 20 (5%) persons with Campylobacter enteritis was cytotoxic for HeLa cells at a titer of 1:40, and 10 (50%) were cytotoxic for CHO cells at maximum titers of 1:20. Cytotoxic activity for CHO cells at a median titer of 1:20 was also present in 40% of the fecal filtrates from persons with diarrhea due to causes other than Campylobacter enteritis, and in 33% of filtrates from healthy, asymptomatic persons. The observed low level of cytotoxicity in fecal filtrates from all patient groups studied likely resulted from non-specific factors, unrelated to the pathogenesis of Campylobacter enteritis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb13993.x
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  • 2
    Electronic Resource
    Electronic Resource
    Role of dprA in transformation of Campylobacter jejuni (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 252 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The role of a dprA ortholog (Cj0634) in Campylobacter jejuni transformation was phenotypically assessed using two strains. C. jejuni strain 11168 was naturally competent for transformation by chromosomal DNA, while efficiency decreased 100-fold in a Cj0634::aphA mutant, whereas C. jejuni strain 480 was not naturally competent. C. jejuni strain 480 but not 11168 could be electro-transformed by shuttle plasmid pRY111, an effect completely abolished by Cj0634 interruption. Complementation of the Cj0634 mutation in C. jejuni strain 480 in trans with vectors containing the dprA homologs from C. jejuni, Helicobacter pylori, or Haemophilus influenzae, completely (for Cj0634) or partially (H. pylori 〉 H. influenzae) restored electro-transformation. Thus, C. jejuni expresses a DprA ortholog that functionally most closely resembles that of H. pylori and is involved in DNA transformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2005.08.052
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of hopQ alleles in East Asian and Western strains of Helicobacter pylori (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 251 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Helicobacter pylori hopQ (omp27) alleles exhibit a high level of genetic diversity, and certain hopQ genotypes have been associated with an increased risk for peptic ulcer disease. In this study, we analyzed hopQ alleles in H. pylori strains from East Asia and the United States. Phylogenetic analysis indicated the presence of two highly divergent families of hopQ alleles, without evidence of extensive recombination. Type I hopQ alleles from Western and Asian H. pylori strains were similar, and markedly different from type II hopQ alleles. Analyses of synonymous and non-synonymous nucleotide substitutions suggested that there is a positive selection for HopQ amino acid diversity. Type II hopQ alleles were identified commonly in Western H. pylori strains, but rarely in East Asian strains. Nearly all of the East Asian strains analyzed were cagA-positive and contained type I hopQ alleles. Geographic variation in the genetic characteristics of H. pylori strains may be a factor contributing to geographic variation in gastric cancer incidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2005.07.023
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  • 4
    Electronic Resource
    Electronic Resource
    Generation of Campylobacter fetus S-layer protein diversity utilizes a single promoter on an invertible DNA segment (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Wild-type strains of Campylobacter fetus contain a monomolecular array of surface layer proteins (SLPs) and vary the antigenicity of the predominant SLP expressed. Reciprocal recombination events among the eight genomic SLP gene cassettes, which encode 97- to 149 kDa SLPs, permit this variation. To explore whether SLP expression utilizes a single promoter, we created mutant bacterial strains using insertional mutagenesis by rescue of a marker from plasmids. Experimental analysis of the mutants created clearly indicates that SLP expression solely utilizes the single sapA promoter, and that for variation C. fetus uses a mechanism of DNA rearrangement involving inversion of a 6.2 kb segment of DNA containing this promoter. This DNA inversion positions the sapA promoter immediately upstream of one of two oppositely oriented SLP gene cassettes, leading to its expression. Additionally, a second mechanism of DNA rearrangement occurs to replace at least one of the two SLP gene cassettes bracketing the invertible element. As previously reported promoter inversions in prokaryotes, yeasts and viruses involve alternate expression of at most two structural genes, the ability of C. fetus to use this phenomenon to express one of multiple cassettes is novel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02469.x
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  • 5
    Electronic Resource
    Electronic Resource
    Overcoming the restriction barrier to plasmid transformation of Helicobacter pylori (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Helicobacter pylori strains demonstrate substantial variability in the efficiency of transformation by plasmids from Escherichia coli, and many strains are completely resistant to transformation. Among the barriers to transformation are numerous strain-specific restriction-modification systems in H. pylori. We have developed a method to protect plasmid DNA from restriction by in vitro site-specific methylation using cell-free extracts of H. pylori before transformation. In two cases, plasmid DNA treated with cell-free extracts in vitro acquired the restriction pattern characteristic of genomic DNA from the source strain. Among three strains examined in detail, the transformation frequency by treated plasmid shuttle and suicide vectors was significantly increased compared with mock-treated plasmid DNA. The results indicate that the restriction barrier in H. pylori can be largely overcome by specific DNA methylation in vitro. The approach described should significantly enhance the ability to manipulate gene function in H. pylori and other organisms that have substantial restriction barriers to transformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02036.x
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  • 6
    Electronic Resource
    Electronic Resource
    Restriction–modification system differences in Helicobacter pylori are a barrier to interstrain plasmid transfer (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Helicobacter pylori cells are naturally competent for the uptake of both plasmid and chromosomal DNA. However, we demonstrate that there are strong barriers to transformation of H. pylori strains by plasmids derived from unrelated strains. We sought to determine the molecular mechanisms underlying these barriers. Transformation efficiency was assessed using pHP1, an Escherichia coli–H. pylori shuttle vector conferring kanamycin resistance. Transformation of 33 H. pylori strains was attempted with pHP1 purified from either E. coli or H. pylori, and was successfully introduced into only 11 strains. Digestion of H. pylori chromosomes with different restriction endonucleases (REs) showed that DNA methylation patterns vary substantially among strains. The strain most easily transformed, JP26, was found to have extremely low endogenous RE activity and to lack a restriction–modification (R–M) system, homologous to MboI, which is highly conserved among H. pylori strains. When we introduced this system to JP26, pHP1 from MboI.M+ JP26, but not from wild-type JP26, transformed MboI R−M+ JP26 and heterologous MboI R−M+ wild-type H. pylori strains. Parallel studies with pHP1 from dam+ and dam−E. coli strains confirmed these findings. These data indicate that the endogenous REs of H. pylori strains represent a critical barrier to interstrain plasmid transfer among H. pylori.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02049.x
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  • 7
    Electronic Resource
    Electronic Resource
    Heterogeneity of Helicobacter pylori cag genotypes in experimentally infected mice (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 203 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Our aim was to assess whether the Helicobacter pylori population recovered from experimentally infected mice show heterogeneity in cag genotypes. Wild-type FVB/N mice were challenged with strain Hp1 and sacrificed 8 weeks later. Direct PCR on gastric tissue was performed using primers for glmM and cagA, and for these two genes and for cagE and virB11 using DNA from the infecting and the emerging strains. The gastric tissues of two of five mice were PCR+ for glmM but not cagA. For the infecting strain, the PCRs for all four genes studied were strongly positive, but the sweeps from the emerging strains from both mice gave weaker signals for cagA and cagE. Examination of single colonies showed reduced or absent signals for cagA and cagE in relation to glmM and virB11. Serial dilution PCR of sweep isolates from the mice showed a 10- to 100-fold decrease in cagA signal compared to the infecting strain. The decrease of cagA and cagE, but not virB11, amplification and lack of cagA hybridization in Southern blots indicates a selective loss of the right half of the cag island during murine infection. This phenomenon is consistent with host-induced adaptive changes of cag genotype in the population of colonizing H. pylori cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10828.x
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  • 8
    Electronic Resource
    Electronic Resource
    Characteristics of Helicobacter pylori natural transformation (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 186 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: For Helicobacter pylori, which exhibits substantial genetic diversity, many strains are naturally competent for transformation by exogenous DNA. To better understand the mechanism of natural transformation and its role in the generation of diversity, we sought to systematically identify factors important for natural transformation in H. pylori. We now show that the highest frequency of H. pylori transformation occurs when DNA is introduced prior to exponential phase growth, and that it is a saturable phenomenon. That transformation can be inhibited by DNA from Helicobacter (H. pylori and Helicobacter bilis) but not Escherichia coli suggests specificity based on DNA source. Finally, the cag island was determined to be unnecessary for high-frequency transformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09117.x
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  • 9
    Electronic Resource
    Electronic Resource
    The equilibria that allow bacterial persistence in human hosts (2007)
    [s.l.] : Nature Publishing Group
    Nature 449 (2007), S. 843-849 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We propose that microbes that have developed persistent relationships with human hosts have evolved cross-signalling mechanisms that permit homeostasis that conforms to Nash equilibria and, more specifically, to evolutionarily stable strategies. This implies that a group of highly diverse ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06198
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  • 10
    Electronic Resource
    Electronic Resource
    IV. Molecular biology of S-layers (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 20 (1997), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this chapter we report on the molecular biology of crystalline surface layers of different bacterial groups. The limited information indicates that there are many variations on a common theme. Sequence variety, antigenic diversity, gene expression, rearrangements, influence of environmental factors and applied aspects are addressed. There is considerable variety in the S-layer composition, which was elucidated by sequence analysis of the corresponding genes. In Corynebacterium glutamicum one major cell wall protein is responsible for the formation of a highly ordered, hexagonal array. In contrast, two abundant surface proteins form the S-layer of Bacillus anthracis. Each protein possesses three S-layer homology motifs and one protein could be a virulence factor. The antigenic diversity and ABC transporters are important features, which have been studied in methanogenic archaea. The expression of the S-layer components is controlled by three genes in the case of Thermus thermophilus. One has repressor activity on the S-layer gene promoter, the second codes for the S-layer protein. The rearrangement by reciprocal recombination was investigated in Campylobacter fetus. 7–8 S-layer proteins with a high degree of homology at the 5′ and 3′ ends were found. Environmental changes influence the surface properties of Bacillus stearothermophilus. Depending on oxygen supply, this species produces different S-layer proteins. Finally, the molecular bases for some applications are discussed. Recombinant S-layer fusion proteins have been designed for biotechnology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6976.1997.tb00304.x
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