ENVIRONMENTAL MICROBIOLOGY

Programmed Death Machines All at Sea

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Science  07 Dec 2012:
Vol. 338, Issue 6112, pp. 1265
DOI: 10.1126/science.338.6112.1265-a

The interaction between viruses and phytoplankton blooms can influence marine carbon export. In culture, it has been established that giant double-stranded DNA coccolithoviruses invoke glycosphingolipid synthesis to trigger programmed cell death in neighboring uninfected cells, thus amplifying lysis. Using mesocosm enclosures in a Norwegian fjord, Vardi et al. probed the dynamics of Emiliania huxleyi and its associated virus at sea. They discovered several conserved molecular correlates for concurrent ecological observations, including release of the same viral death-inducing lipids that had been observed in culture. The viral glycosphingolipids induce intracellular reactive oxygen species, which prompt the programmed cell death machinery in algal cells to assemble, providing an environment that includes everything the virus needs for successful replication. Furthermore, the stressed algal cells produce expolymer particles that form aggregates called marine snow, and it is this that accelerates carbon export to deep water. Finally, virus infection induces a subset of the algal cells to form haploid sexual stages that can evade infection and live to die another year.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1208895109 (2012).

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