Genomic diversity of Helicobacter pylori populations from different regions of the human stomach.

Abstract

Individuals infected with Helicobacter pylori harbour unique and diverse populations of quasispecies, but diversity between and within different regions of the human stomach and the process of bacterial adaptation to each location are not yet well understood. We applied whole-genome deep sequencing to characterise the within- and between- stomach region genetic diversity of H. pylori populations from paired antrum and corpus biopsies of 15 patients, along with single biopsies from one region of 3 patients, by scanning allelic diversity. We combined population deep sequencing with more conventional sequencing of multiple H. pylori single colony isolates from individual biopsies to generate a unique dataset. Single colony isolates were used to validate the scanning allelic diversity pipelines. We detected extensive population allelic diversity within the different regions of each patients stomach. Diversity was most commonly found within non-coding, hypothetical, outer membrane, restriction modification system, virulence, lipopolysaccharide biosynthesis, efflux systems and chemotaxis-associated genes. Antrum and corpus populations from the same patient grouped together phylogenetically, indicating that most patients were initially infected with a single strain, which then diversified. Single colonies from the antrum and corpus of the same patients grouped into distinct clades, suggesting mechanisms for within-location adaptation across multiple H. pylori isolates from different patients. Recombination was observed both within and between different regions of the same stomach. The comparisons made available by combined sequencing and analysis of isolates and populations enabled comprehensive analysis of the genetic changes associated with H. pylori diversification and stomach region adaptation.