Mechanisms that create genetic diversity in <i>H. pylori</i>.

<p>Colored arrows represent different genes, and the correspondingly colored triangles, rectangles, and circles represent the proteins encoded by these genes. Diversification mechanisms (right side of figure) include spontaneous point mutations, slipped-strand mispairing, and intragenomic recombination. Allelic changes involving nonsynonymous point mutations and mosaic genes resulting from intragenomic recombination can alter the function and/or the antigenic epitopes of the encoded protein. Gene expression can also be regulated by gene conversion resulting from intragenomic recombination, and phase variation mediated by slipped-strand mispairing. Reassortment of genes (left side of figure) by natural transformation with exogenous DNA also contributes to genetic diversity. Natural transformation with DNA from a superinfecting strain, for example, can introduce new genes and new alleles of already present genes (horizontal gene transfer). Similarly, natural transformation with DNA from a variant clone of the same strain can further propagate an advantageous allele acquired by within-genome diversification.