Fig 1. Phylogenetic tree of Helicobacter pylori nucleotide sequences, including the vacA m region.

Genetic distances were estimated using the six-parameter method, and phylogenetic trees were constructed using the neighbor-joining method. Reference strains are shown with strain names and GenBank accession numbers. Bootstrap values are shown along each main branch of the tree. The lengths of the horizontal bars indicate the number of nucleotide substitutions per site.