Environmental Determinants of Transformation Efficiency in Helicobacter pylori

Moore, M. H.; Lam, Anna M.; Bhatnagar, Srijak; Solnick, Jay V.

doi:10.1128/jb.00633-13

Cited by 15 publications

(16 citation statements)

References 44 publications

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“…This assay is not only dependent on the competent state but also on downstream effects like timely expression of the cassette and survival of the microaerobic bacterium under selection conditions. In addition to resistance marker expression, the transcription of a subset of genes essential for natural transformation was characterized in other studies [ 37 , 38 ]. Here we directly monitor active DNA uptake by covalently labelling λ DNA with a Cy3 fluorophore and microscopically tracking DNA import in single cells.…”

Section: Resultsmentioning

confidence: 99%

“…Transcriptome analysis previously indicated transcriptional repression of two essential genes for natural transformation ( comB8 and comH ) at pH 5.4 relative to neutral growth conditions [ 49 ]. A recent study also hinted towards an effect of pH on natural transformation [ 38 ]. The authors conducted the experiments on agar plates, supplemented with a pH indicator.…”

Section: Discussionmentioning

confidence: 99%

“…Interestingly, increased transformation rate was observed for H . pylori grown on agar plates incubated at slightly increased pH or different atmospheric composition [ 38 ].…”

Section: Introductionmentioning

confidence: 99%

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Genetic Diversity as Consequence of a Microaerobic and Neutrophilic Lifestyle

et al. 2016

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As a neutrophilic bacterium, Helicobacter pylori is growth deficient under extreme acidic conditions. The gastric pathogen is equipped with an acid survival kit, regulating urease activity by a pH-gated urea channel, opening below pH 6.5. After overcoming acid stress, the bacterium’s multiplication site is situated at the gastric mucosa with near neutral pH. The pathogen exhibits exceptional genetic variability, mainly due to its capability of natural transformation, termed competence. Using single cell analysis, we show here that competence is highly regulated in H. pylori. DNA uptake complex activity was reversibly shut down below pH 6.5. pH values above 6.5 opened a competence window, in which competence development was triggered by the combination of pH increase and oxidative stress. In contrast, addition of sublethal concentrations of the DNA-damaging agents ciprofloxacin or mitomycin C did not trigger competence development under our conditions. An oxygen-sensitive mutant lacking superoxide dismutase (sodB) displayed a higher competent fraction of cells than the wild type under comparable conditions. In addition, the sodB mutant was dependent on adenine for growth in broth and turned into non-cultivable coccoid forms in its absence, indicating that adenine had radical quenching capacity. Quantification of periplasmically located DNA in competent wild type cells revealed outstanding median imported DNA amounts of around 350 kb per cell within 10 min of import, with maximally a chromosomal equivalent (1.6 Mb) in individual cells, far exceeding previous amounts detected in other Gram-negative bacteria. We conclude that the pathogen’s high genetic diversity is a consequence of its enormous DNA uptake capacity, triggered by intrinsic and extrinsic oxidative stress once a neutral pH at the site of chronic host colonization allows competence development.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Genetic Diversity as Consequence of a Microaerobic and Neutrophilic Lifestyle

et al. 2016

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“…For example, in the Gram-positive bacterium Streptococcus pneumoniae, competence (and therefore singlestrand availability through DNA uptake) is induced by an antibiotic stress response (109). In the Gram-negative human pathogen, Helicobacter pylori, competence is increased in conditions of low CO 2 and high pH (110).…”

Section: Single-strand Pathwaymentioning

confidence: 99%

The Integron: Adaptation On Demand

Loot²,

et al. 2015

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The integron is a powerful system which, by capturing, stockpiling, and rearranging new functions carried by gene encoding cassettes, confers upon bacteria a rapid adaptation capability in changing environments. Chromosomally located integrons (CI) have been identified in a large number of environmental Gram-negative bacteria. Integron evolutionary history suggests that these sedentary CIs acquired mobility among bacterial species through their association with transposable elements and conjugative plasmids. As a result of massive antibiotic use, these so-called mobile integrons are now widespread in clinically relevant bacteria and are considered to be the principal agent in the emergence and rise of antibiotic multiresistance in Gram-negative bacteria. Cassette rearrangements are catalyzed by the integron integrase, a site-specific tyrosine recombinase. Central to these reactions is the single-stranded DNA nature of one of the recombination partners, the attC site. This makes the integron a unique recombination system. This review describes the current knowledge on this atypical recombination mechanism, its implications in the reactions involving the different types of sites, attC and attI, and focuses on the tight regulation exerted by the host on integron activity through the control of attC site folding. Furthermore, cassette and integrase expression are also highly controlled by host regulatory networks and the bacterial stress (SOS) response. These intimate connections to the host make the integron a genetically stable and efficient system, granting the bacteria a low cost, highly adaptive evolution potential "on demand".

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“…Briefly, 244 base pairs upstream of the babA translational start site and 39 base pairs of 5′ babA gene sequence were replaced with a CAT_rpsL cassette in a streptomycin resistant strain of H. pylori J166, using the plasmid pBabA as previously described39. The CAT_rpsL cassette was amplified using primers RpsLF and CamR (Table 2)36.…”

Section: Methodsmentioning

confidence: 99%

Host Determinants of Expression of the Helicobacter pylori BabA Adhesin

Kable

Hansen

Styer

et al. 2017

Sci Rep

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Expression of the Helicobacter pylori blood group antigen binding adhesin A (BabA) is more common in strains isolated from patients with peptic ulcer disease or gastric cancer, rather than asymptomatic colonization. Here we used mouse models to examine host determinants that affect H. pylori BabA expression. BabA expression was lost by phase variation as frequently in WT mice as in RAG2−/− mice that do not have functional B or T cells, and in MyD88−/−, TLR2−/− and TLR4−/− mice that are defective in toll like receptor signaling. The presence of other bacteria had no effect on BabA expression as shown by infection of germ free mice. Moreover, loss of BabA expression was not dependent on Leb expression or the capacity of BabA to bind Leb. Surprisingly, gender was the host determinant most associated with loss of BabA expression, which was maintained to a greater extent in male mice and was associated with greater bacterial load. These results suggest the possibility that loss of BabA expression is not driven by adaptive immunity or toll-like receptor signaling, and that BabA may have other, unrecognized functions in addition to serving as an adhesin that binds Leb.

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Environmental Determinants of Transformation Efficiency in Helicobacter pylori

Cited by 15 publications

References 44 publications

Genetic Diversity as Consequence of a Microaerobic and Neutrophilic Lifestyle

Genetic Diversity as Consequence of a Microaerobic and Neutrophilic Lifestyle

The Integron: Adaptation On Demand

Host Determinants of Expression of the Helicobacter pylori BabA Adhesin

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