To explain this fusion behavior, we reason that the membranes are composed of two types of domains -monolayers of O-shaped lipids and bilayers of U-shaped lipids. Formation of U-shaped bilayer domains is likely dictated by the conformational flexibility of the hydrocarbon region in GDGT-0 lipids which allows the lipids to fold in the middle. Previous reports suggest that viral fusion peptides can induce inverted non-lamellar phases in phosphoethanolamine lipids which are known to form hexagonal phases at high temperatures. Similarly, the tendency of GDGT-0 lipids to form inverted non-lamellar phases further allows dehydration of the lipid headgroups upon interaction with influenza viral fusion peptide to stabilize various intermediates key to fusion. Examples from archaeal biology indeed support the idea that GDGT-0 lipids have a greater tendency to adopt U-shapes and play a pivotal role in membrane dynamics. For instance, it has been observed that archaeal viruses such as SSV1 consist of a disproportionately larger fraction (68.1%) of GDGT-0 lipids as compared to its host Sulfolobus solfataricus (0.8%). The presence of high fraction of GDGT-0 lipids in the viral membranes likely facilitates their fusion with the host membranes both during entry and budding.