Helicobacter pylori: Genetics, Recombination, Population Structure, and Human Migrations

Abstract

Humans and their stomach bacterium Helicobacter pylori share a coevolutionary relationship that spans at least the last 100,000 years and quite possibly even longer. Population and evolutionary genetic research has demonstrated a species-wide phylogeographic structure that faithfully mirrors that of its human host. However, because of its very high genetic diversity and fast generation time, H. pylori DNA sequences are often better able to resolve prehistoric human migrations than human DNA markers. The worldwide genetic diversity of H. pylori has, thus far, been divided into 7 populations and 14 subpopulations, most of which are now established markers for recent and prehistoric human migrations. Key developments such as the inference of hypothetical ancestral populations and the implementation of coalescent models have provided a clearer understanding of the population historical role of admixture and recombination and helped superimpose a chronology onto the human H. pylori association, from which the timing, direction, and magnitude of migration events can be accurately inferred. However, there remain large parts of the world from which H. pylori has never been cultured, and this, along with a move to sequence whole genomes rather than just housekeeping genes, will form the basis of future evolutionary genetic research.