A gastric pathogen that is arguably the most nickel-dependent human pathogen known. Two of its key virulence factors—Urease and [NiFe] Hydrogenase—require Nickel, and the bacterium has evolved an elaborate nickel trafficking, storage, and regulation system to support them.

Evidence map4 cited passagesInspect provenance +
01
Urease

Roles beyond acid neutralization: - Required for persistence even at neutral gastric pH. - Promotes angiogenesis. - Stimulates pro-inflammatory cytokines (neutrophil/monocyte chemotaxis). - Binds Class II MHC on gastric epithelial cells → induces apoptosis. - Disrupts epithelial tight junctions (via ammonia production → myosin activation). - Activates blood

02
Clinical Significance

Eradication therapy often includes bismuth—which competes with nickel transport via NiuBDE.

03
Connections

gerd—controversial relationship; H. pylori eradication may worsen reflux in some patients

04
Connections

Contrast with: nickel causes cancer in host cells via epigenetics, while in H. pylori it enables cancer via CagA

Contents1. Nickel-Dependent Virulence Factors2. Nickel Trafficking System3. Clinical Significance4. Connections

Nickel-Dependent Virulence Factors#

Urease#

Up to 10% of total proteome. Essential for in vivo survival: hydrolyzes Urea → Ammonia + bicarbonate, buffering cytoplasmic pH to near-neutral in the Acidic Microenvironment of the stomach. Roles beyond acid neutralization.[1]Role of Nickel in Microbial PathogenesisRobert J. Maier, Stéphane L. Benoit · 2019Open reference 1 ↓

Required for persistence even at neutral gastric pH. Promotes angiogenesis. Stimulates pro-inflammatory cytokines (neutrophil/monocyte chemotaxis).

Binds Class II MHC on gastric epithelial cells → induces apoptosis. Disrupts epithelial tight junctions (via ammonia production → myosin activation). Activates blood platelets (lipoxygenase-mediated pathway).

Alters mucin gene expression.

Holo-urease (nickel (Ni)-bound): catalytic urea hydrolysis + non-catalytic oxidant quenching (Met/Met-sulfoxide cycle with MSR repair). Apo-urease (nickel-free): retains only oxidant-quenching activity. Only 2-25% of urease is actually nickel-activated; the rest may serve the antioxidant role.

[NiFe] Hydrogenase#

Single H₂-uptake type (hydABCDE operon). H₂ is chronically available in the stomach (dissolved H₂ ~80 μM; enzyme Km ~1.8 μM—always saturated). Powers CagA translocation: the carcinogenic effector.

Hydrogenase deletion mutants cannot translocate CagA and do not induce gastric cancer in gerbils.

Enables H₂-stimulated CO₂ fixation (mixotrophy)—a growth mode never before described in a human pathogen. Strains from cancer patients have higher hydrogenase activity than gastritis-only strains.

Nickel Trafficking System#

Transport#

NiuBDE (ABC-type): the only transporter operating at both acidic and neutral pH. Can also transport cobalt/bismuth (relevant to bismuth-based eradication therapy). NixA (NiCoT-type): secondary, nickel (Ni)-only.

Required in vivo (nixA mutants cannot colonize mouse stomachs) but nixA mutants retain some colonization in other models. TonB-dependent FrpB4 for outer membrane transport.

Storage#

Hpn: 47% Histidine, 20-mer binding 5 nickel (Ni)(II)/monomer. Present in all gastric Helicobacter. Primary nickel reservoir.

HpnI (Hpn-like): 25% histidine. Restricted to H. pylori and H. acinonychis. Both compete for nickel under limiting conditions.

Recent discovery: storage proteins interact with a wide array of metabolic proteins—AmiE (aliphatic amidase), PepA (aminopeptidase), and maturation proteins. Suggests a central hub role in nickel metabolism far beyond simple storage.

Regulation#

NikR: nickel-responsive transcriptional regulator controlling urease and hydrogenase expression. Fur: iron-responsive regulator that also influences hyd gene expression.

Export#

  • CznABC: cobalt-zinc-nickel efflux pump. Critical for nickel homeostasis and in vivo colonization.

Clinical Significance#

Infects ~50% of the global population. Causes gastritis, peptic ulcers, Gastric Adenocarcinoma, and MALT lymphoma. Eradication therapy often includes Bismuth—which competes with nickel transport via NiuBDE.[1]Role of Nickel in Microbial PathogenesisRobert J. Maier, Stéphane L. Benoit · 2019Open reference 1 ↓

HspA (GroES homolog with His-rich nickel (Ni)-binding C-terminus) has been explored as a vaccine candidate—partial protection in mice via intranasal administration.

Connections#

  • Metal-Dependent Virulence—nickel (Ni)-urease and [NiFe]-hydrogenase are the paradigmatic metal-dependent virulence factors
  • Nickel—essential cofactor for its two main virulence factors
  • Nutritional Immunity (Metal Sequestration)—host calprotectin/lactoferrin may restrict nickel availability
  • Metal Carcinogenesis—H. pylori-mediated gastric cancer is linked to hydrogenase-powered CagA translocation
  • Gastric Cancer—H. pylori is the primary causative organism; nickel-dependent metalloenzymes power the cancer cascade
  • Gastroesophageal Reflux Disease (GERD)—controversial relationship; H. pylori eradication may worsen reflux in some patients[2]Causal relationship between Helicobacter pylori antibodies and gastroesophageal reflux disease (GERD): A mendelian studyChen J, Zhang J, Ma X et al. · 2023Open reference 2 ↓[3]Analysis of gastric microbiota and Helicobacter pylori infection in gastroesophageal reflux diseaseSugihartono T, Fauzia KA, Miftahussurur M et al. · 2022Open reference 3 ↓[4]Effects of Helicobacter pylori Infection on the Oral Microbiota of Reflux Esophagitis PatientsLiang T, Liu F, Liu L et al. · 2021Open reference 4 ↓
  • Contrast with:[5]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 5 ↓ nickel causes cancer in host cells via epigenetics, while in H. pylori it enables cancer via CagA
Generated evidence record

References 7

Numbered by first appearance in the article, then reconciled with its declared source list.

  1. 1

    ★Robert J. Maier, Stéphane L. Benoit (2019). Role of Nickel in Microbial Pathogenesis. Inorganics.

  2. 2

    Chen J, Zhang J, Ma X et al. (2023). Causal relationship between Helicobacter pylori antibodies and gastroesophageal reflux disease (GERD): A mendelian study. PLoS ONE.

  3. 3

    Sugihartono T, Fauzia KA, Miftahussurur M et al. (2022). Analysis of gastric microbiota and Helicobacter pylori infection in gastroesophageal reflux disease. Gut Pathogens.

  4. 4

    Liang T, Liu F, Liu L et al. (2021). Effects of Helicobacter pylori Infection on the Oral Microbiota of Reflux Esophagitis Patients. Frontiers in Cellular and Infection Microbiology.

  5. 5

    Konstantin Salnikov, Anatoly Zhitkovich (2008). Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and Chromium. Chemical Research in Toxicology.

  6. 6

    Maurya AP, Rajkumari J, Bhattacharjee A et al. (2020). Development, spread and persistence of antibiotic resistance genes (ARGs) in the soil microbiomes through co-selection. Reviews on Environmental Health.

  7. 7

    Campanale M, Nucera E, Ojetti V et al. (2014). Nickel Free-Diet Enhances the Helicobacter pylori Eradication Rate: A Pilot Study. Digestive Diseases and Sciences.

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Article network

Current recordHelicobacter pyloriMicroorganisms
MechanismsUreaseMutually connected recordsMechanismsHydrogenaseMutually connected recordsMetalsNickelMutually connected recordsMechanismsUreaMutually connected recordsMechanismsAmmoniaMutually connected recordsMechanismsAcidic MicroenvironmentReferenced in this microorganisms recordMechanismsTight JunctionsReferenced in this microorganisms recordMechanismsCagAMutually connected recordsMechanismsNickel TransportersMutually connected recordsMechanismsHistidineMutually connected recordsDiseasesGastric UlcerMutually connected recordsDiseasesGastric AdenocarcinomaMutually connected records
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