scholarly journals Quantitative Effect of luxS Gene Inactivation on the Fitness of Helicobacter pylori

2006 ◽  
Vol 72 (10) ◽  
pp. 6615-6622 ◽  
Author(s):  
Woo-Kon Lee ◽  
Keiji Ogura ◽  
John T. Loh ◽  
Timothy L. Cover ◽  
Douglas E. Berg
Keyword(s):  
Helicobacter Pylori ◽  
Competitive Ability ◽  
Reference Strain ◽  
Bacterial Species ◽  
Soft Agar ◽  
Autoinducer 2 ◽  
Methyl Cycle ◽  
Adenosyl Methionine ◽  
Unrelated Strain ◽  
H Pylori

ABSTRACT Furanone metabolites called AI-2 (autoinducer 2), used by some bacterial species for signaling and cell density-regulated changes in gene expression, are made while regenerating S-adenosyl methionine (SAM) after its use as a methyl donor. The luxS-encoded enzyme, in particular, participates in this activated methyl cycle by generating both a pentanedione, which is transformed chemically into these AI-2 compounds, and homocysteine, a precursor of methionine and SAM. Helicobacter pylori seems to contain the genes for this activated methyl cycle, including luxS, but not genes for AI-2 uptake and transcriptional regulation. Here we report that deletion of luxS in H. pylori reference strain SS1 diminished its competitive ability in mice and motility in soft agar, whereas no such effect was seen with an equivalent ΔluxS derivative of the unrelated strain X47. These different outcomes are consistent with H. pylori's considerable genetic diversity and are reminiscent of phenotypes seen after deletion of another nonessential metabolic gene, that encoding polyphosphate kinase 1. We suggest that synthesis of AI-2 by H. pylori may be an inadvertent consequence of metabolite flux in its activated methyl cycle and that impairment of this cycle and/or pathways affected by it, rather than loss of quorum sensing, is deleterious for some H. pylori strains. Also tenable is a model in which AI-2 affects other microbes in H. pylori's gastric ecosystem and thereby modulates the gastric environment in ways to which certain H. pylori strains are particularly sensitive.

scholarly journals Slow Genetic Divergence of Helicobacter pylori Strains during Long-Term Colonization

2005 ◽  
Vol 73 (8) ◽  
pp. 4818-4822 ◽  
Author(s):  
Annelie Lundin ◽  
Britta Björkholm ◽  
Ilya Kupershmidt ◽  
Magnus Unemo ◽  
Peter Nilsson ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Genetic Divergence ◽  
Bacterial Species ◽  
Pcr Amplification ◽  
Genetic Change ◽  
Genetic Changes ◽  
Single Strain ◽  
Divergent Gene ◽  
Asymptomatic Adult ◽  
H Pylori

ABSTRACT The genetic variability of Helicobacter pylori is known to be high compared to that of many other bacterial species. H. pylori is adapted to the human stomach, where it persists for decades, and adaptation to each host results in every individual harboring a distinctive bacterial population. Although clonal variants may exist within such a population, all isolates are generally genetically related and thus derived from a common ancestor. We sought to determine the rate of genetic change of H. pylori over 9 years in two asymptomatic adult patients. Arbitrary primed PCR confirmed the relatedness of individual subclones within a patient. Furthermore, sequencing of 10 loci (∼6,000 bp) in three subclones per time and patient revealed only two base pair changes among the subclones from patient I. All sequences were identical among the patient II subclones. However, PCR amplification of the highly divergent gene amiA revealed great variation in the size of the gene between the subclones within each patient. Thus, both patients harbored a single strain with clonal variants at both times. We also studied genetic changes in culture- and mouse-passaged strains, and under both conditions no genetic divergence was found. These results suggest that previous estimates of the rate of genetic change in H. pylori within an individual might be overestimates.

scholarly journals The Quorum-Sensing Molecule Autoinducer 2 Regulates Motility and Flagellar Morphogenesis in Helicobacter pylori

2007 ◽  
Vol 189 (17) ◽  
pp. 6109-6117 ◽  
Author(s):  
Bethany A. Rader ◽  
Shawn R. Campagna ◽  
Martin F. Semmelhack ◽  
Bonnie L. Bassler ◽  
Karen Guillemin
Keyword(s):  
Helicobacter Pylori ◽  
Quorum Sensing ◽  
Sigma Factor ◽  
Critical Role ◽  
Soft Agar ◽  
Dependent Manner ◽  
Flagellar Gene ◽  
Wild Type ◽  
Autoinducer 2 ◽  
Mutant Phenotypes

ABSTRACT The genome of the gastric pathogen Helicobacter pylori contains a homologue of the gene luxS, which has been shown to be responsible for production of the quorum-sensing signal autoinducer 2 (AI-2). We report here that deletion of the luxS gene in strain G27 resulted in decreased motility on soft agar plates, a defect that was complemented by a wild-type copy of the luxS gene and by the addition of cell-free supernatant containing AI-2. The flagella of the luxS mutant appeared normal; however, in genetic backgrounds lacking any of three flagellar regulators—the two-component sensor kinase flgS, the sigma factor σ28 (also called fliA), and the anti-sigma factor flgM—loss of luxS altered flagellar morphology. In all cases, the double mutant phenotypes were restored to the luxS + phenotype by the addition of synthetic 4,5-dihydroxy-2,3-pentanedione (DPD), which cyclizes to form AI-2. Furthermore, in all mutant backgrounds loss of luxS caused a decrease in transcript levels of the flagellar regulator flhA. Addition of DPD to luxS cells induced flhA transcription in a dose-dependent manner. Deletion of flhA in a wild-type or luxS mutant background resulted in identical loss of motility, flagella, and flagellar gene expression. These data demonstrate that AI-2 functions as a secreted signaling molecule upstream of FlhA and plays a critical role in global regulation of flagellar gene transcription in H. pylori.

scholarly journals Growth Phase Regulation of flaA Expression in Helicobacter pylori Is luxS Dependent

2004 ◽  
Vol 72 (9) ◽  
pp. 5506-5510 ◽  
Author(s):  
John T. Loh ◽  
Mark H. Forsyth ◽  
Timothy L. Cover
Keyword(s):  
Helicobacter Pylori ◽  
Growth Phase ◽  
Wild Type ◽  
Phase Dependence ◽  
Autoinducer 2 ◽  
Extracellular Signaling ◽  
Reporter Strains ◽  
Phase Regulation ◽  
H Pylori

ABSTRACT LuxS plays a role in the synthesis of an extracellular signaling molecule, autoinducer 2 (AI-2). To analyze a possible role of AI-2 in regulating Helicobacter pylori gene expression, we constructed a panel of transcriptional reporter strains. We show that the expression of H. pylori flaA is growth phase dependent and that flaA transcription increases in association with increased culture density. Mutating the luxS gene eliminates growth-phase-dependent control of flaA, and this growth phase dependence is restored when the luxS mutant strain is complemented with the wild-type luxS gene.

scholarly journals Molecular and Structural Analysis of the Helicobacter pylori cag Type IV Secretion System Core Complex

mBio ◽  
2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Arwen E. Frick-Cheng ◽  
Tasia M. Pyburn ◽  
Bradley J. Voss ◽  
W. Hayes McDonald ◽  
Melanie D. Ohi ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Bacterial Species ◽  
Secretion System ◽  
Effector Proteins ◽  
Type Iv Secretion ◽  
Secretion Systems ◽  
Core Complex ◽  
Type Iv ◽  
Membrane Spanning ◽  
H Pylori

ABSTRACT Bacterial type IV secretion systems (T4SSs) can function to export or import DNA, and can deliver effector proteins into a wide range of target cells. Relatively little is known about the structural organization of T4SSs that secrete effector proteins. In this report, we describe the isolation and analysis of a membrane-spanning core complex from the Helicobacter pylori cag T4SS, which has an important role in the pathogenesis of gastric cancer. We show that this complex contains five H. pylori proteins, CagM, CagT, Cag3, CagX, and CagY, each of which is required for cag T4SS activity. CagX and CagY are orthologous to the VirB9 and VirB10 components of T4SSs in other bacterial species, and the other three Cag proteins are unique to H. pylori . Negative stain single-particle electron microscopy revealed complexes 41 nm in diameter, characterized by a 19-nm-diameter central ring linked to an outer ring by spoke-like linkers. Incomplete complexes formed by Δ cag3 or Δ cagT mutants retain the 19-nm-diameter ring but lack an organized outer ring. Immunogold labeling studies confirm that Cag3 is a peripheral component of the complex. The cag T4SS core complex has an overall diameter and structural organization that differ considerably from the corresponding features of conjugative T4SSs. These results highlight specialized features of the H. pylori cag T4SS that are optimized for function in the human gastric mucosal environment. IMPORTANCE Type IV secretion systems (T4SSs) are versatile macromolecular machines that are present in many bacterial species. In this study, we investigated a T4SS found in the bacterium Helicobacter pylori. H. pylori is an important cause of stomach cancer, and the H. pylori T4SS contributes to cancer pathogenesis by mediating entry of CagA (an effector protein regarded as a “bacterial oncoprotein”) into gastric epithelial cells. We isolated and analyzed the membrane-spanning core complex of the H. pylori T4SS and showed that it contains unique proteins unrelated to components of T4SSs in other bacterial species. These results constitute the first structural analysis of the core complex from this important secretion system.

scholarly journals Interplay and cooperation of Helicobacter pylori and gut microbiota in gastric carcinogenesis

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Seyedeh Zahra Bakhti ◽  
Saeid Latifi-Navid
Keyword(s):  
Helicobacter Pylori ◽  
Gut Microbiota ◽  
Intestinal Microbiota ◽  
Bacterial Species ◽  
Short Chain Fatty Acids ◽  
Gastric Carcinogenesis ◽  
Oncogenic Signaling ◽  
Comprehensive Overview ◽  
H Pylori ◽  
Oncogenic Signaling Pathways

AbstractChronic Helicobacter pylori infection is a critical risk factor for gastric cancer (GC). However, only 1–3 % of people with H. pylori develop GC. In gastric carcinogenesis, non-H. pylori bacteria in the stomach might interact with H. pylori. Bacterial dysbiosis in the stomach can strengthen gastric neoplasia development via generating tumor-promoting metabolites, DNA damaging, suppressing antitumor immunity, and activating oncogenic signaling pathways. Other bacterial species may generate short-chain fatty acids like butyrate that may inhibit carcinogenesis and inflammation in the human stomach. The present article aimed at providing a comprehensive overview of the effects of gut microbiota and H. pylori on the development of GC. Next, the potential mechanisms of intestinal microbiota were discussed in gastric carcinogenesis. We also disserted the complicated interactions between H. pylori, intestinal microbiota, and host in gastric carcinogenesis, thus helping us to design new strategies for preventing, diagnosing, and treating GC.

scholarly journals Gastric Microbiota in Helicobacter pylori-Negative and -Positive Gastritis Among High Incidence of Gastric Cancer Area

Cancers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 504 ◽  
Author(s):  
Boldbaatar Gantuya ◽  
Hashem B. El-Serag ◽  
Takashi Matsumoto ◽  
Nadim J. Ajami ◽  
Khasag Oyuntsetseg ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Helicobacter Pylori ◽  
Bacterial Species ◽  
Rrna Gene ◽  
Linear Discriminant ◽  
Haemophilus Parainfluenzae ◽  
Increased Risk ◽  
Comparison Groups ◽  
H Pylori ◽  
Gastric Microbiota

Helicobacter pylori (H. pylori) related chronic gastritis is a well-known major etiological factor for gastric cancer development. However, H. pylori-negative gastritis (HpN) is not well described. We aimed to examine gastric mucosal microbiota in HpN compared to H. pylori-positive gastritis (HpP) and H. pylori-negative non-gastritis group (control). Here, we studied 11 subjects with HpN, 40 with HpP and 24 controls. We performed endoscopy with six gastric biopsies. Comparison groups were defined based on strict histological criteria for the disease and H. pylori diagnosis. We used 16S rRNA gene amplicon sequencing to profile the gastric microbiota according to comparison groups. These results demonstrate that the HpP group had significantly lower bacterial richness by the operational taxonomic unit (OTU) counts, and Shannon and Simpson indices as compared to HpN or controls. The linear discriminant analysis effect size analysis showed the enrichment of Firmicutes, Fusobacteria, Bacteroidetes and Actinobacteria at phylum level in the HpN group. In the age-adjusted multivariate analysis, Streptococcus sp. and Haemophilus parainfluenzae were at a significantly increased risk for HpN (odds ratio 18.9 and 12.3, respectively) based on abundance. Treponema sp. was uniquely found in HpN based on occurrence. In this paper, we conclude that Streptococcus sp., Haemophilus parainfluenzae and Treponema sp. are candidate pathogenic bacterial species for HpN. These results if confirmed may have important clinical implications.

scholarly journals Identification of the periplasmic DNA receptor for natural transformation of Helicobacter pylori

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Prashant P. Damke ◽  
Anne Marie Di Guilmi ◽  
Paloma Fernández Varela ◽  
Christophe Velours ◽  
Stéphanie Marsin ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Natural Transformation ◽  
Bacterial Species ◽  
Dna Binding Protein ◽  
Gram Negative Bacteria ◽  
Membrane Channel ◽  
Inner Membrane ◽  
Double Stranded Dna ◽  
Periplasmic Domain ◽  
H Pylori

AbstractHorizontal gene transfer through natural transformation is a major driver of antibiotic resistance spreading in many pathogenic bacterial species. In the case of Gram-negative bacteria, and in particular of Helicobacter pylori, the mechanisms underlying the handling of the incoming DNA within the periplasm are poorly understood. Here we identify the protein ComH as the periplasmic receptor for the transforming DNA during natural transformation in H. pylori. ComH is a DNA-binding protein required for the import of DNA into the periplasm. Its C-terminal domain displays strong affinity for double-stranded DNA and is sufficient for the accumulation of DNA in the periplasm, but not for DNA internalisation into the cytoplasm. The N-terminal region of the protein allows the interaction of ComH with a periplasmic domain of the inner-membrane channel ComEC, which is known to mediate the translocation of DNA into the cytoplasm. Our results indicate that ComH is involved in the import of DNA into the periplasm and its delivery to the inner membrane translocator ComEC.

scholarly journals Impact of Helicobacter pylori resistance in unsuccessfully pluritreated patients in a Department of Infectious Diseases in Rome

2010 ◽  
Vol 1 (1) ◽  
pp. 3
Author(s):  
Maria Teresa Mascellino ◽  
Barbara Porowska ◽  
Rosa Nicosia ◽  
Alessandra Oliva ◽  
Priscilla Boccia ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Resistance Rate ◽  
Test Method ◽  
Resistance Testing ◽  
Antibiotic Resistant ◽  
Diffusion Technique ◽  
Resistant Strains ◽  
Unrelated Strain ◽  
H Pylori ◽  
Rapid Emergence

Twenty-five pluritreated patients were examined. Fifty-six percent yielded Helicobacter pylori (H. Pilory); of these, 9 patients showed a concomitant colonization of the three gastric regions. The highest resistance rate was found for metronidazole (71.8%) followed by chlaritromycin (53.1%). Amoxycillin showed the best susceptibility (only 6% of resistance), tetracycline showed 12% of resistant strains and levofloxacin appeared to be a promising antibacterial agent (18% of resistance). The E-test method was shown to be more suitable than disk diffusion technique for resistance testing. Combined resistance to both chlaritromycin and metronidazole appeared in 50% of the strains. The isolates showing this dual resistance are known to be difficult to eradicate. Resistotypes were shown to be genotypically different even if the strains with the resistance to both chlaritromycin and metronidazole are more likely to belong to genotype cagA+ and vacA s1m1. Heteroresistance (different susceptibility of the isolated strains in a single stomach) resulted in 36% of patients with pangastritis. Indeed, the concomitant presence of H. pylori strains in the same subject, either susceptible or resistant or vice versa, may interfere with the eradication outcomes. In our study, antibiotic resistant H. pylori typically develops from pre-existing susceptible strains rather than from co-infection with a different and unrelated strain. In fact, each pair of isolates detected in our 4 patients with heteroresistance belonged to the same genotype (cagA+ s1m2 in patient 1 and cagA+ s1m1 in patients 2, 3 and 4). In conclusion, H. pylori antibiotic resistance does present several issues in pluritreated patients owing to the rapid emergence of multi-resistant strains.

scholarly journals Helicobacter pylori perceives the quorum-sensing molecule AI-2 as a chemorepellent via the chemoreceptor TlpB

Microbiology ◽  
2011 ◽  
Vol 157 (9) ◽  
pp. 2445-2455 ◽  
Author(s):  
Bethany A. Rader ◽  
Christopher Wreden ◽  
Kevin G. Hicks ◽  
Emily Goers Sweeney ◽  
Karen M. Ottemann ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Double Mutant ◽  
Soft Agar ◽  
Dependent Manner ◽  
Wild Type ◽  
Environmental Chemical ◽  
Single Mutant ◽  
Autoinducer 2 ◽  
Reduced Frequency ◽  
H Pylori

Helicobacter pylori moves in response to environmental chemical cues using a chemotaxis two-component signal-transduction system. Autoinducer-2 (AI-2) is a quorum-sensing signal produced by the LuxS protein that accumulates in the bacterial environment in a density-dependent manner. We showed previously that a H. pylori luxS mutant was defective in motility on soft agar plates. Here we report that deletion of the luxS gene resulted in swimming behaviour with a reduced frequency of stops as compared to the wild-type strain. Stopping frequency was restored to wild-type levels by genetic complementation of the luxS mutation or by addition of synthetic 4,5-dihydroxy-2,3-pentanedione (DPD), which cyclizes to form AI-2. Synthetic DPD also increased the frequency of stops in wild-type H. pylori, similar to the behaviour induced by the known chemorepellent HCl. We found that whereas mutants lacking the chemoreceptor genes tlpA, tlpC or tlpD responded to an exogenous source of synthetic DPD, the chemoreceptor mutant tlpB was non-responsive to a gradient or uniform distribution of the chemical. Furthermore, a double mutant lacking both tlpB and luxS exhibited chemotactic behaviour similar to the tlpB single mutant, whereas a double mutant lacking both tlpB and the chemotransduction gene cheA behaved like a nonchemotactic cheA single mutant, supporting the model that tlpB functions in a signalling pathway downstream of luxS and upstream of cheA. We conclude that H. pylori perceives LuxS-produced AI-2 as a chemorepellent via the chemoreceptor TlpB.

scholarly journals Agent-Based Modeling Demonstrates How Local Chemotactic Behavior Can Shape Biofilm Architecture

2018 ◽  
Author(s):  
Emily G. Sweeney ◽  
Andrew Nishida ◽  
Alexandra Weston ◽  
Maria S. Bañuelos ◽  
Kristin Potter ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Three Dimensional ◽  
Structural Features ◽  
Agent Based Modeling ◽  
Emergent Properties ◽  
Cellular Interactions ◽  
Biofilm Growth ◽  
Agent Based ◽  
Autoinducer 2 ◽  
H Pylori

AbstractMature bacterial biofilms have elaborate three-dimensional architectures that endow these structures with their durability and resistance to environmental perturbations. We used agent-based modeling to explore whether local cellular interactions were sufficient to give rise to global structural features of biofilms. Specifically, we asked whether chemorepulsion from a self-produced quorum-sensing molecule, autoinducer-2 (AI-2), was sufficient to recapitulate biofilm growth and cellular organization observed for biofilms of the human pathogen Helicobacter pylori. To carry out this modeling, we modified an existing platform, Individual-based Dynamics of Microbial Communities Simulator (iDynoMiCS), to incorporate three-dimensional chemotaxis, planktonic cells that could join or leave the biofilm structure, and cellular production of AI-2. We simulated biofilm growth of previously characterized H. pylori strains with varying AI-2 production and sensing capacities. Using biologically plausible parameters, we were able to recapitulate both the variation in biofilm mass and cellular distributions observed with these strains. Specifically, the strains that were competent to chemotax away from AI-2 produced smaller and more heterogeneously spaced biofilms, whereas the AI-2 chemotaxis defective strains produced larger and more homogeneously spaced biofilms. The model also provided new insights into the cellular demographics contributing to the biofilm patterning of each strain. Our analysis supports the idea that cellular interactions at small spatial and temporal scales are sufficient to give rise to larger scale emergent properties of biofilms.ImportanceMost bacteria exist in aggregated, three-dimensional structures called biofilms. Biofilms are resistant to antimicrobials and can pose societal problems, for example when they grow in plumbing systems or on medical implants. Understanding the processes that promote the growth and disassembly of biofilms could lead to better strategies to manage these structures. We had previously shown that Helicobacter pylori bacteria are repulsed by high concentrations of a self-produced molecule, autoinducer-2 (AI-2) and that H. pylori mutants deficient in AI-2 sensing form larger and more homogeneously spaced biofilms. Here we used computer simulations of biofilm formation to show that local H. pylori behavior of repulsion from high AI-2 could explain the overall architecture of H. pylori biofilms. Our findings demonstrate that it is possible to change global biofilm organization by manipulating local cell behaviors, which suggests that simple strategies targeting cells at local scales could be useful for controlling biofilms in industrial and medical settings.

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