Aflagellated mutants of <i>Helicobacter pylori</i> generated by genetic transformation of naturally competent strains using transposon shuttle mutagenesis

Haas, Rainer; Meyer, Thomas F.; Putten, J. P. M. Van

doi:10.1111/j.1365-2958.1993.tb01618.x

Cited by 171 publications

(158 citation statements)

References 38 publications

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“…The cassette was in the nonpolar orientation as determined by restriction enzyme digestion (data not shown). The mutant construct pHP0479GmK.1 was used to generate HP0479 mutant strains of 26695, SS1, O:3, ATCC 43504 (type strain), and PJ1 (16). In all strains, the incorporation of the mutant HP0479 allele by double recombination was confirmed by PCR (data not shown).…”

Section: Resultsmentioning

confidence: 99%

Identification of a d - glycero - d - manno -Heptosyltransferase Gene from Helicobacter pylori

et al. 2005

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Section: Resultsmentioning

confidence: 99%

Identification of a d - glycero - d - manno -Heptosyltransferase Gene from Helicobacter pylori

et al. 2005

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“…Transformation of H. pylori strains was performed with plasmid or chromosomal DNA according to a procedure described previously (22). Bacteria were harvested from serum plates and suspended to an optical density at 550 nm (OD 550 ) of 0.1 in brucella broth containing 10% fetal calf serum.…”

Section: Methodsmentioning

confidence: 99%

Functional and Topological Characterization of Novel Components of the comB DNA Transformation Competence System in Helicobacter pylori

Karnholz¹,

Hoefler²,

Odenbreit³

et al. 2006

J Bacteriol

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Helicobacter pylori is one of the most diverse bacterial species known. A rational basis for this genetic variation may be provided by its natural competence for genetic transformation and high-frequency recombination. Many bacterial competence systems have homology with proteins that are involved in the assembly of type IV pili and type II secretion systems. In H. pylori, DNA uptake relies on a transport system related to type IV secretion systems (T4SS) designated the comB system. The prototype of a T4SS in Agrobacterium tumefaciens consists of 11 VirB proteins and VirD4, which form the core unit necessary for the delivery of single proteins or large nucleoprotein complexes into target cells. In the past we identified proteins ComB4 and ComB7 through ComB10 as being involved in the process of DNA uptake in H. pylori. In this study we identified and functionally characterized further (T4SS-homologous) components of the comB transformation competence system. By combining computer prediction modeling, experimental topology determination, generation of knockout strains, and genetic complementation studies we identified ComB2, ComB3, and ComB6 as essential components of the transformation apparatus, structurally and functionally homologous to VirB2, VirB3, and VirB6, respectively. comB2, comB3, and comB4 are organized as a separate operon. Thus, for the H. pylori comB system, all T4SS core components have been identified except for homologues to VirB1, VirD4, VirB5, and VirB11.Helicobacter pylori, a highly motile gram-negative bacterial pathogen, is the principal cause of chronic active gastritis and peptic ulcer disease in humans and has been implicated in the development of gastric mucosa-associated lymphoid tissue lymphoma and adenocarcinoma (38,49). H. pylori colonizes a very special habitat at the surface of gastric epithelial cells or in the mucus layer covering the epithelium, which suggests that this bacterium has evolved specialized features for gastric adaptation. A comparison of the two published genome sequences shows considerable diversity in gene content, with about 7% of all putative genes being strain specific (2). The panmictic population structure of H. pylori is believed to result from frequent recombination during mixed colonization by unrelated strains (20,50).H. pylori is naturally competent for genetic transformation (36). Natural transformation competence in bacteria is a complex process, involving DNA binding, uptake/translocation, and recombination. In general, bacterial competence systems have homology with proteins that are involved in the assembly of type IV pili and type II secretion systems and form a structure that partially spans the cell envelope (see reference 13 for a recent review). In H. pylori, DNA uptake is not mediated by a type IV pilus-based apparatus but relies on a transport system related to type IV secretion systems (T4SS) designated the comB system (26).The Vir system of Agrobacterium tumefaciens, necessary for the transfer of its transferred DNA (T-DNA) into plant ce...

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“…The H. pylori strains G27 (21), PMSS1 and SS1 (22), J99 (ATCC number 700824), P1 (23), and 60190 (ATCC number 49503) were grown on Wilkins-Chalgren blood agar plates under microaerobic conditions (10% CO 2 , 5% O 2 , 85% N 2 , and 37˚C).…”

Section: Bacterial Strains and Culture Conditionsmentioning

confidence: 99%

Helicobacter pylori Cytotoxin-Associated Gene A Impairs Human Dendritic Cell Maturation and Function through IL-10–Mediated Activation of STAT3

Kaebisch

Mejías-Luque

Prinz

et al. 2014

The Journal of Immunology

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Helicobacter pylori infection induces chronic gastric inflammation that can progress to cancer. In this process, the virulence factor cytotoxin-associated gene A (CagA) plays a central role by directly altering epithelial cell signaling and inducing a strong Th1 immune response, which contributes to carcinogenesis. It is still barely understood how the bacterium evades clearance despite this solid immune response and persists lifelong. Dendritic cells (DCs) play a major role in determining the adaptive immune response toward H. pylori, and high levels of regulatory T cells have been detected infiltrating the gastric mucosa of H. pylori–infected patients, which contribute to bacterial persistence. Although murine studies indicate that H. pylori induces tolerization of DCs and impairs DC maturation, the virulence determinants involved are still controversial. Moreover, the signaling cascades engaged in human DC tolerization upon H. pylori infection remain unknown. In the current study, we analyzed the effect of H. pylori infection on human DC maturation and function, focusing on the virulence factors implicated and signaling pathways involved. Our results reveal that CagA is crucial for DC tolerization by modulating IL-10 secretion and, in turn, STAT3 phosphorylation, favoring a regulatory T cell immune response. Our findings help to unravel the paradox why CagA-positive strains, although eliciting a stronger inflammatory response, have overcome evolutionary pressure and persisted in their human host.

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Aflagellated mutants of Helicobacter pylori generated by genetic transformation of naturally competent strains using transposon shuttle mutagenesis

Cited by 171 publications

References 38 publications

Identification of a d - glycero - d - manno -Heptosyltransferase Gene from Helicobacter pylori

Identification of a d - glycero - d - manno -Heptosyltransferase Gene from Helicobacter pylori

Functional and Topological Characterization of Novel Components of the comB DNA Transformation Competence System in Helicobacter pylori

Helicobacter pylori Cytotoxin-Associated Gene A Impairs Human Dendritic Cell Maturation and Function through IL-10–Mediated Activation of STAT3

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