- Helicobacter pylori strain G27 is a well-studied clinical isolate that has become a widely used model system for molecular and cellular microbiology, particularly in genetic studies and functional analyses of virulence mechanisms.
- G27 was isolated in the United States from a patient with duodenal ulcer disease and belongs to the hpEurope population, which is predominant in Western countries.
- What sets G27 apart from other commonly used strains is its robust genetic tractability, high natural competence for DNA uptake, and its amenability to transformation. These features make it a favored strain for generating isogenic mutants, performing allelic exchange, and conducting structure-function studies of virulence genes and regulatory networks.
- G27 possesses a fully functional cag pathogenicity island (cagPAI), encoding a type IV secretion system (T4SS) that delivers the CagA oncoprotein into host gastric epithelial cells. The CagA protein in G27 is of the Western-type, containing EPIYA-A, -B, and -C motifs that become tyrosine-phosphorylated upon translocation. Once inside the host cell, phosphorylated CagA interacts with host proteins like SHP-2 and triggers signaling cascades that promote cytoskeletal rearrangements, pro-inflammatory cytokine production (e.g., IL-8), and altered cell polarity. These processes are key contributors to H. pylori–induced gastric disease and carcinogenesis. The G27 T4SS is highly active, making this strain particularly useful for dissecting the molecular interactions between H. pylori and host cell signaling machinery.
- In addition to CagA, G27 produces Vacuolating cytotoxin A (VacA) with the s1/m1 genotype, which corresponds to a highly active form of the toxin. VacA in G27 causes prominent vacuolation of epithelial cells, disrupts mitochondrial function, and modulates immune cell responses by impairing T-cell proliferation and antigen presentation. Together, the activities of CagA and VacA allow G27 to model both acute and chronic effects of H. pylori infection. G27 also expresses important adhesins, including HopQ, BabA, and SabA, which mediate adherence to host epithelial cells and facilitate CagA translocation via interactions with host CEACAMs. These adhesins also play roles in tissue tropism and immune modulation.
- G27 has been a cornerstone strain for exploring bacterial secretion systems, protein-protein interactions, and host-pathogen dynamics. Its ease of manipulation has made it a preferred background for studying genetic regulation of the cagPAI, the structure and assembly of the T4SS pilus, and the trafficking of effector proteins. Importantly, G27 is one of the few strains for which live-cell imaging studies of T4SS function have been extensively performed, helping to visualize the physical interactions between the bacterium and host cell surfaces in real time. Additionally, variants such as G27-MA (mouse-adapted) have been used to extend in vitro findings into in vivo systems, although the original G27 strain itself is not naturally adapted for murine colonization.
- In summary, H. pylori strain G27 is a genetically versatile and virulent strain that serves as a powerful tool for understanding the molecular biology of H. pylori infection. With a functional cagPAI, potent VacA activity, and strong adherence properties, it models key aspects of H. pylori-induced pathogenesis. Its high transformability and compatibility with modern genetic tools make it particularly valuable for reverse genetics, live-cell imaging, and functional genomics. G27 remains a mainstay in the toolkit of H. pylori researchers focused on mechanistic and translational aspects of gastric disease.
