Hanon McShea

Abstract The first eukaryotic cell originated through the union of an archaeon (Asgardarchaeota) and a bacterium (Alphaproteobacteria). Little is known about the molecular basis of eukaryogenesis, but it is likely that lipids played a key role in this process. Modern eukaryotic membranes contain polycyclic triterpenoids (mainly sterols) that are essential for a variety of cellular functions, but these lipids have not been identified in archaea.

Abstract Cyclic terpenoids are a class of lipid compounds containing immense structural and functional diversity, with many cyclic triterpenoids acting as membrane components, and, for a few well-studied molecules, regulators of membrane physical properties and spatial organization. Cyclic terpenoids are also readily preserved as terpane fossils, such as steranes and hopanes, which form a rich record of the evolution of life on Earth.