Emiliania huxleyi Goes Viral: Dynamic Variation of Intact Polar Lipids and Alkenones
Abstract
Viruses are an important component of marine ecosystems, shunting more than 25% of the organic carbon in algal biomass away from grazers to the dissolved organic carbon pool, fueling microbial foodwebs. Virus infection has long been implicated in the termination of Emiliania huxleyi blooms, and recent work demonstrated that EhV86, the type virus of E. huxleyi, is bound by a lipid membrane and employs an animal-like infection strategy, similar to the human immunodeficiency virus (HIV). We add to this story by quantifying EhV86 and host (Ehux374) lipodomes before, during, and after infection in laboratory culture. We identified novel intact polar lipids (IPLs), and based on their structures and experimental results, we hypothesize that they are dynamic players in cell-virus interactions, not just structural membrane components. Alkenones also have an apparent role in viral infection as they are part of the EhV86 lipidome, their production increases during infection, and growth temperatures calculated from alkenone unsaturation in infected cultures are elevated relative to uninfected cultures. EhV86 carries genes for glycosphingolipid (GSL) synthesis, and production increases exponentially during infection, leading to a ca. 100-fold increase in GSL concentration per cell. We hypothesize that specific GSLs (1) promote viral attachment via a sialic acid headgroup and (2) induce programmed cell death and lysis. In response to infection, Ehux374 produces a diacylglycerolipid with a myriocin-like (ML) structure that inhibits GSL synthesis. Remarkably, the EhV86 lipidome contains an abundant ML, but with a different fatty acid distribution that apparently neutralizes its effect on the GSL synthesis pathway. The neutralized ML lipid is also common in lipid extracts from the North Atlantic, suggesting it may be found in other organisms as well. We propose that much of the lipid variability during infection occurs in lipid rafts, microdomains in the plasma membrane targeted by viruses for cell entry and exit. The alkenones along with the rest of the EhV86 lipidome may come from lipid rafts or intracellular membranes, supporting the view that alkenones have a structural role in membranes and are not just energy storage molecules.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMOS13C1757F
- Keywords:
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- 0460 BIOGEOSCIENCES / Marine systems;
- 4850 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL / Marine organic chemistry;
- 4855 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL / Phytoplankton