Microevolution in Helicobacter pylori

Abstract

Helicobacter pylori chronically colonises the human gastric mucosa. It is a major cause of chronic active gastritis and peptic ulcer disease and is associated with the development of gastric neoplasia. The population structure of H. pylori is characterised by a high level of genetic diversity. This diversity arises from increased mutation and frequent recombination in the genome of the organism. H. pylori is naturally competent for transformation which facilitates acquisition of DNA by horizontal transfer. The non-clonal nature of the H. pylori population structure means that distinct isolates are recovered from each colonised individual and, generally, no clonal relationship can be discerned between epidemic logically unrelated isolates. Furthermore, isolates taken from the gastric niche of a single individual have also been shown to exhibit genomic 'microevolution', manifest as small differences in DNA fingerprint profiles between strains when discriminatory fingerprinting methods were utilised. In the present studies chromosomal rearrangement between paired isolates of H. pylori was characterised with respect to defined loci and by whole-genome examination.