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If you had to guess the most abundant organism on the whole planet, you’d probably think of ants or, maybe, bacteria. But a newly discovered virus might trump them all.

Pelagibacter ubique is often cited as the most common organism ever: it’s a third of all the single-celled organisms in the ocean. But, as is always the case, something eats P. unique. In fact, four different viruses parasitize this one species. Researchers at Oregon State University recently discovered these viruses and concluded that the one of them that was the most common. The Economist reports:

[OSU's Stephen Giovannoni] then compared their DNA with databases of DNA found in seawater from around the world, to find out how abundant each is. The upshot was that a virus dubbed HTVC010P was the commonest. It thus displaces its host as the likely winner of the most-common-living-thing prize.

There’s a little debate here about whether or not a virus can even, in principle, dethrone P. ubique. The Economist explains:

That does depend, of course, on your definition of “living thing”. Some biologists count viruses as organisms. Some do not. The reason is that a virus relies for its growth and reproduction on the metabolic processes of the cell it infects. This means viruses themselves are hard to parasitise, since they do no work on which another organism can free-ride. Which is why the next two lines of Swift’s poem, “And these have smaller fleas to bite ’em/And so proceed ad infinitum”, are wrong—and why, because HTVC010P itself can have no parasites, it probably really is the commonest organism on the planet.

But if you accept viruses as living organisms, HTVC01P is certainly the king.

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