Bacterial gene import and mesophilic adaptation in archaea

It is widely believed that the archaeal ancestor was hyperthermophilic, but during archaeal evolution, several lineages - including haloarchaea and their sister methanogens, the Thaumarchaeota, and the uncultured Marine Group II and Marine Group III Euryarchaeota (MGII/III) - independently adapted to lower temperatures. Recent phylogenomic studies suggest that the ancestors of these lineages were recipients of massive horizontal gene transfer...