Lipid biomarkers for viral infection of marine phytoplankton

Viruses are the most abundant biological entity in the marine environment and serve as major evolutionary and biogeochemical drivers in the ocean. Algae-infecting viruses are estimated to turn over more than a quarter of the photosynthetically fixed carbon. Tapping into the arms race between an algal host and its virus can reveal unique strategies of viral infectivity and host defence. An ecologically important marine host-virus model system is the cosmopolitan alga Gephyrocapsa huxleyi and its specific virus, G. huxleyi virus (EhV), a large dsDNA virus. G. huxleyi forms massive blooms that cover vast oceanic areas and are frequently terminated due to infection by EhV. EhV infection causes profound remodeling of the G. huxleyi lipidome, including the production of structurally distinct virus-derived glycosphingolipid (vGSL), which were found to be central components of the EhV membrane and to trigger host programmed cell death.

In this presentation, I will share our approach to study the involvement of lipids in G. huxleyi-EhV interactions across scales, from the lab to the natural environment. By applying LC-MS- and imaging-MS-based lipidomics methodologies, we were able to map the lipidomic landscape during infection, to characterize the lipid makeup of the different components that are present during infection (cells, virions, extracellular vesicles), and to identify novel lipid biomarkers for virus-resistant cells. Recently, we utilized our diverse lipid biomarkers to characterize small subpopulations of infected cells within resistant populations, revealing the phenotypic heterogeneity that drives this host-virus coexistence in nature. Taken together, and combined with complementary methods, this work deepens our understanding of the role of lipids in host-virus interactions.