Did Bacteria, Archaea, And Eukaryotes Exchange Transporter Genes Appreciably During The Past Two Billion Years?
After analyzing dozens of large transport protein families, we find several examples of horizontal transfer between distinct kingdoms within these domains, such as between gram-positive and gram-negative bacteria. However, we find little evidence of horizontal transfer of transporter genes among the three domains occurring any time during the past two billion years. Thus, although hundreds of members of the MC family are found in eukaryotes, not a single such member is found in a prokaryote. Moreover, of the hundreds of sequenced homologues of the phosphoenolpyruvate, sugar phosphotransferase system (PTS), every one is in a bacterium, without a single example in an archaeon or a eukaryote.
