Sasiri Juliana Vargas Urbano, University of Delaware

Homeocurvature adaptation of phospholipids underlies pressure-specialization of deep-sea invertebrates

The deep ocean is dark, cold, and pressurized — pressure increases by 1 bar for every 10 m depth. How does marine life adapt to this extreme environment? Given that lipid membranes are sensitive to both temperature and pressure (they are the most compressible biological material in a cell), one expects to find adaptations in the lipidomes of organisms that are specialized for life at high pressure. Here, we explore this question using the ctenophores as a model organism. Ctenophores make up a marine invertebrate phylum that is the oldest distinct lineage on the metazoan tree, and different species have adapted independently to many pressure and temperature regimes. Building on years of work by the Haddock lab collecting different ctenophore species from different marine environments, and on recent work by the Budin lab obtaining ctenophore lipidomes, we use MD simulations to study how ctenophore lipidomes adapt to maintain critical material properties within a narrow range. We find that depth strongly predicts plasmalogen abundance, with deep-adapted ctenophore lipidomes containing as much as 73 mol % phosphatidylethanolamine plasmalogen. Our simulations and analysis suggest that plasmalogen maintains membrane deformability at high pressure so that vital cellular functions (eg, endo- and exocytosis) can still be performed under deep-sea conditions. These results imply that in addition to other more widely appreciated membrane properties (such as fluidity), lipid intrinsic curvature is also subject to natural selection in the deep sea.