Abstract

GUTIERREZ-ESCOBAR, Andrés Julián. MOLECULAR EVOLUTIONARY ANALYSIS OF ADHERENCE: EVIDENCE OF POSITIVE SELECTION OPERATING ON AlpAB LOCUS AND horB ADHESINS OF Helicobacter pylori. rev.udcaactual.divulg.cient. [online]. 2013, vol.16, n.1, pp.3-15. ISSN 0123-4226.

The adherence to the epithelial gastric cell is a key step in the physiopathology of Helicobacter pylori infection. There are several outer membrane proteins involved in the adherence that are expressed in a sequential fashion, meanwhile the attachment to the host cell takes place. Currently, the adhesins AlpA, AlpB and HorB have attracted the attention because of i) its role in the adherence, ii) The differential activation of intracellular pathways in the gastric host epithelial cell between Asian and European strains and iii) in its role in the fitness according to gene deletion studies. It is largely known that H. pylori have a global distribution with regional divergent populations that have evolved following host conditions. Here, it was indentified that the evolutionary history of alpA, alpB and HorB adhesins followed a birth and death evolution model under purifying selection in which the deleterious mutations have been actively purged from the population allowing the fixation of beneficial changes for the fitness. It was detected based on permutation tests that H. pylori´s populations from America-Europe (FsT0.51395.) and Asia-Europe (FsT 0.46030) for alpA and the populations from America-Europe (FsT 0.43711) for alpB present a significant genetic differentiation mediated by positive selection as suggest by the MKT test results. Finally, it was found using PAML that a 9.51% of alpA, a 8.5% of alpB and a 5% of HorB proteins evolved under strong specific positive selection following linage specific geographic patterns.

Keywords : Adhesion; AlpAB locus; molecular evolution; positive selection; Red Queen hypothesis; coevolution.

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