The membrane of LUCA: an ‘archaeal/bacterial’ model?

Abstract

Archaea typically produce isoprenoid-based ether-linked glycerol-1-phosphate (G1P) membrane lipids, whereas Bacteria/ Eukarya usually produce membrane lipids that constitute fatty acids ester-bound to glycerol-3-phosphate (G3P). The emergence of the two distinct lipid variants (generally referred to as the ‘lipid divide’) represents a crucial event in early evolution, as it likely ushered in the evolvement of the two primordial domains, the Archaea and the Bacteria. This automatically suggests that the Last Universal Common Ancestor (LUCA) was at the origin of the lipid divide. While the nature of the primordial membrane is yet to be resolved, a popular theory is that LUCA’s membrane composed both archaeal and bacterial lipids. In the current paper, I summarize our present understanding of the features of the primordial membrane. By recounting recently published genomic and experimental data, I examine the possibility that LUCA possessed an heterochiral ‘archaeal/bacterial’ membrane before the lipid divide came to be.