Horizontal Gene Transfers from Bacteria toEntamoebaComplex: A Strategy for Dating Events along Species Divergence

Abstract

Horizontal gene transfer has proved to be relevant in eukaryotic evolution, as it has been found more often than expected and related to adaptation to certain niches. A relatively large list of laterally transferred genes has been proposed and evaluated for the parasiteEntamoeba histolytica. The goals of this work were to elucidate the importance of lateral gene transfer along the evolutionary history of some members of the genusEntamoeba, through identifying donor groups and estimating the divergence time of some of these events. In order to estimate the divergence time of some of the horizontal gene transfer events, the dating of someEntamoebaspecies was necessary, following an indirect dating strategy based on the fossil record of plausible hosts. The divergence betweenE. histolyticaandE. nuttalliiprobably occurred 5.93 million years ago (Mya); this lineage diverged fromE. dispar9.97 Mya, while the ancestor of the latter separated fromE. invadens68.18 Mya. We estimated times for 22 transferences; the most recent occurred 31.45 Mya and the oldest 253.59 Mya. Indeed, the acquisition of genes through lateral transfer may have triggered a period of adaptive radiation, thus playing a major role in the evolution of theEntamoebagenus.