Prokaryotes bridging the lipid divide

The fundamental biochemical and stereochemical difference in how cell membrane lipids are built between Archaea on one side, and Bacteria and Eukarya on the other is known as the lipid divide. It is often assumed to translate in the impossibility of combining membranes of both types. It was established early when little sampling of the biodiversity was available. Since then, exceptions have been revealed and accumulated. Here, we review those exceptions and complement them with a broad survey, revealing diverse bacteria with mixed membrane-lipid features. Together with liposome assays and synthetic-biology experiments, studies on these organisms suggest that the lipid divide can be bridged. We conclude by discussing the evolutionary implications for LUCA, the origin of the prokaryotic domains and eukaryogenesis.