The early evolution of lipid membranes and the three domains of life.

All cell membranes are composed of glycerol phosphate phospholipids, and this commonality argues for the presence of such phospholipids in the last common ancestor, or cenancestor. However, phospholipid biosynthesis is very different between bacteria and archaea, leading to the suggestion that the cenancestor was devoid of phospholipid membranes. Recent phylogenomic studies challenge this view, suggesting that the cenancestor did possess complex phospholipid membranes. Here, we discuss the implications of these recent findings for membrane evolution in archaea and bacteria, and for the origin of the eukaryotic cell.