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You wanted to know: what is this virus that infects the phytoplankton? (Part One)

The views expressed are those of the author and are not necessarily those of Scientific American.


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So far I’ve told you about the phytoplankton we’re studying — the coccolithophores, how we figure out where they’re going to be, and how we collect them. But there’s a key element that’s missing in this description: the virus that infects them. And a lot of you wanted to know about it.

What kind of viruses are in the ocean? Are they the same as viruses on land? Todd from New York

Viruses are the most abundant biological thing in the ocean, but we know very little about them. For a long time, people thought phytoplankton were very long-lived. They died when they were eaten, or floated down too deep, but otherwise scientists couldn’t figure out what would make the little plants die. Turns out viruses kill lots of phytoplankton.

There are probably hundreds of thousands of marine viruses that we’ve never even seen before. Generally, marine viruses are different from the ones we find on land, simply because they infect different kinds of organisms — marine ones. The science team onboard the Knorr does know something about the particular virus we’re looking for, though.

What virus are they investigating that is infecting Emiliania huxleyi? Are they going to isolate this and attempt a genome? Gaytana Balestrier from Willingboro

The virus in question is called a coccolithovirus (fitting, since it infects coccolithophores). It’s really big (as far as viruses go) — about 160-180 nanometers in diameter. That’s about twice the size of the human flu virus. In fact, the coccolithovirus that these scientists are looking for has the largest genome of any marine virus. It has 472 genes that code for proteins. By comparison, the influenza virus only has 8 protein-coding genes.

Two different genomes from viruses that infect Ehux were sequenced in 2005. In total, nine different coccolithovirus genomes have been sequenced so far, each one infecting a different species of coccolithophore. The one that infects Ehux is called Emiliania huxleyi virus 86, or EhV-86 for short.

 

Two Ehux cells: on the left a healthy one, on the right a cell full of viruses.

How was the relationship between this phytoplankton and its virus first found? Brenda Wright from Salt Lake City

In 1999, a marine biologist named Willie Wilson observed the Ehux virus for the first time. In the years following, he and other biologists – including some of the ones on this ship – found this intriguing interaction between the coccolithophores and the virus. (To hear Willie explain the epic battle between phytoplankton and viruses on Radiolab, click here.)

Before we get to what’s cool about this virus in particular, we have to talk about what usually happens during viral infection. Viruses are pretty much bundles of DNA or RNA packaged inside some kind of protein shell. They can come in all shapes, sizes, and configurations.

Unlike the cells that make up plants and animals, viruses don’t replicate through cell division. They don’t have all the parts they need. Remember, they’re just a ball of genetic material. So instead, they hijack their host’s cells. A virus will attach onto a healthy cell, and inject a little packet of genetic material into the host. It then uses the cells machinery to replicate itself over and over again. Eventually, most viruses cause the cell to lyse, or burst.

To be continued. Come back tomorrow to find out how this particular virus infects Ehux.

 

During this trip, I’ll be answering your questions about the science, this boat, and life onboard. Want to know how we search for plankton, why we’re here, or what the food is like? Just ask me! And if you’re wondering how I got here, check out the groups that made this adventure possible: Mind Open Media and COSEE NOW.

Previously in this series:

All Aboard: how you can be a part of our research blog
You wanted to know: what are these phytoplankton?
You wanted to know: what am I bringing to sea?
Greetings from Ponta Delgada! We set sail tomorrow.
Steaming North: how the scientists are trying to find plankton
The superstar sensor: what is a CTD?
Status Update: Day 3 at the Cyclonic Eddy

Rose Eveleth About the Author: Rose Eveleth is a producer, designer, writer and animator based in Brooklyn. She's got a degree in ecology from U.C. San Diego, and a masters in journalism from NYU. Now, she makes sciencey stuff for places like The New York Times, Scientific American, Story Collider and OnEarth. Follow on Twitter @roseveleth.

The views expressed are those of the author and are not necessarily those of Scientific American.





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