Figure 4.

Genetic factors leading to an increase in virulence of Helicobacter pylori. a) Small subunit rRNA phylogenetic consensus tree of bacterial species in the human digestive system related to H.pylori, showing the recent acquisition of cagA; b), the EPIYA domains that are present in the cagA gene and the evolution of the EPIYA-D domains in the asian lineages. Tree (a) was constructed as described in Methods, numerals indicate posterior probabilities, tree (b) as in Figure 1.