Pan-genome and core genome among <i>Helicobacter pylori</i>.

<p>(A) Histogram showing the distribution of the number of strains in each OG among the 30 strains. Sets of OGs corresponding to pan-genome, universal core, accessory, and unique OGs are indicated. (B) Sizes of the syntenic core, universal core, and pan-genome as functions of the number of strains. An ordered lists of the 30 strains was randomly generated and the sets of <i>n</i> strains (<i>n</i> = 2,4,…,30) generated from this list was subject to core- and pan-genome analysis. The test was repeated 20 times and the average numbers of core- and pan-genome sizes were plotted with error bars that represent standard deviations. Syntenic core between two genomes is not well defined and thus is not plotted. (C) The number of new OGs added to the pan-genome as a function of the number of strains. The number of new OG in <i>n</i> strains (<i>n</i> = 4,6,…,30) was calculated as the difference between the pan-genome size in <i>n</i> strains and that in <i>n–</i> 2 strains.