Helicobacter pylori genome evolution during human infection.
Lynn Kennemann1, Xavier Didelot, Toni Aebischer
1Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, 30625 Hannover, Germany.
Summary
Helicobacter pylori exhibits high genetic diversity through recombination, acquiring DNA fragments that influence outer membrane genes. The H. pylori genome remains stable without mixed infections, showing selection on adhesin genes during colonization.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Helicobacter pylori is a significant gastric pathogen known for its substantial genetic diversity.
- Understanding the mechanisms driving this diversity is crucial for combating H. pylori infections.
Purpose of the Study:
- To investigate the genomic changes and recombination patterns in Helicobacter pylori strains.
- To compare genome stability in chronically infected individuals versus experimentally infected volunteers.
Main Methods:
- Whole-genome comparisons using 454 sequencing technology.
- Analysis of single nucleotide polymorphisms (SNPs) and DNA fragment import (recombination) in H. pylori strains.
- Examination of gene families, particularly the hop family involved in adhesion.
Main Results:
- Significant genetic variation, including isolated SNPs and imported DNA clusters, was observed in H. pylori from chronically infected Colombians.
- Recombination events involved uptake of long DNA fragments, often in groups, with increased frequency in hop family genes.
- Minimal genomic differences and no evidence of recombination were found in H. pylori from an experimentally infected volunteer, indicating genome stability without mixed infection.
- An OFF/ON switch in the hopZ adhesin gene suggests strong in vivo selection during early colonization.
Conclusions:
- Helicobacter pylori maintains high genetic diversity through non-random DNA fragment import and recombination, particularly affecting adhesion-related genes.
- The H. pylori genome demonstrates stability in the absence of mixed infections, with evidence of strong selection on specific genes like hopZ during colonization.
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