Genetic and functional characterization of Helicobacter pylori virulence factors of the 5300-year-old ice mummy Ötzi

• Applicant: Dr. Bodo Linz
• Subject Area: Medical Microbiology and Mycology, Hygiene, Molecular Infection Biology ; General Genetics and Functional Genome Biology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 580733453

The human stomach bacterium Helicobacter pylori colonizes the stomach of over 50% of the world's population. Once colonized, humans typically develop a chronic infection that often persists through most of the host’s life. While most people remain asymptomatic, the infection can progress in a subset of patients into chronic gastritis, ulcers and even adenocarcinoma or MALT lymphoma. The outcome of an infection is influenced by many elements, including host genetics and life style as well as the genotype of the pathogen, particularly its virulence factors. Among others, pathogenicity of H. pylori is attributed to the cag pathogenicity island (cagPAI)-encoded type-IV secretion system (T4SS) and its effector protein CagA, the vacuolating cytotoxin VacA, adhesins such as the blood group antigen binding protein BabA, and serine protease HtrA. Sequences of bacterial pathogens associated with ancient human remains are of exceptional interest in the scientific community. The mummified corpse of the Tyrolean Iceman, commonly known as “Ötzi”, is a largely intact and naturally preserved mummy of a European from the Neolithic Copper Age. Analysis of the stomach region revealed that Ötzi was infected with H. pylori. Extensive sequencing of stomach content samples allowed the reconstruction of this 5300-year-old H. pylori genome. However, despite outstanding progress in the sequencing and assembly of ancient bacterial genomes and the detection of virulence genes such as cagA, there is no information on the pathogenic function of those ancient microbes. In this proposal, we will show a practicable strategy of how to analyze virulence factors of a long extinct pathogen and will thus bridge the wide gap between paleo(meta)genomics and the large available arsenal of assays for the analysis of virulence mechanisms. We will generate mutant H. pylori laboratory strains that carry genes of virulence factors HtrA, CagA and the structural T4SS component CagL of the Ötzi H. pylori strain and will evaluate single, double and triple gene mutants in various functional tests in comparison to the isogenic parental strains. The genetic and functional characterization of virulence factors of the 5,300-year-old Ötzi H. pylori will provide valuable insight into the function of these ancient virulence factors and their pathogenicity-associated mechanisms. Analysing the Ötzi H. pylori virulence factors in a functional manner will shed light on whether this ancient H. pylori already used the same virulence mechanisms known from modern strains and will allow to reconstruct the evolution of pathogenicity in this gastric bacterium. Thus, our project will show a feasible strategy of how to functionally characterize virulence factors detected in metagenome data from ancient bacteria and will provide proof of principle of the approach.

• DFG Programme: Research Grants