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Go to Brilliant.org/SciShow to learn how you can bring your STEM skills to the next level next year. [♪ INTRO]. Viruses are small.

Like really, really, really small. So you might think nothing could survive on a virus-based diet. But, according to a growing body of research, the right kind of microorganism can.

And that means, while viruses certainly cause their fair share of disease and death, they may also give life to key players in the planet’s smallest ecosystems. Even though we can’t see them, there are a lot of viruses out there. Researchers estimate there’s more than 200 million tons of virus-based carbon in the world.

For perspective, all of the world’s humans weigh in at around 60 million tons of carbon. And it turns out that, gram for gram, viruses are actually pretty rich in nitrogen, carbon, and phosphorus, which are important nutrients for microbes. So it kind of makes sense for something to eat them — assuming that something is small enough.

And that’s where tiny organisms called protists come in. Protists have sophisticated cells like we do, but they aren’t animals, or plants, or fungi — they’re in a kingdom all their own. Many of them can be found in the ocean and in seabed sediments alongside lots of viruses.

And some, called picozoa, are super small— we’re talking around 3 microns in size. A few different researchers have suggested these wee little protists may eat viruses, since they’re small enough that the viruses could actually be filling. But they didn’t really have a good way of showing this happens.

I mean, 3 microns is small enough that no one can really watch these critters eat. So, to figure out if protists eat viruses, the researchers behind a 2020 Frontiers in Microbiology study did the next best thing. They split open a bunch of sea dwelling protists and looked at the genetic material inside them.

That’s basically the single-cell equivalent of cutting open a stomach and examining the contents. And they found a surprisingly large amount of viral genetic material in the protists they sampled. Exactly how much varied, but what really stood out was that all of the smallest protists had viral genetic material inside them.

So the researchers think they frequently or even exclusively eat viruses. Now, since the team was working with a snapshot of what’s inside the protists, they can’t say for sure that they ate the viruses, as opposed to the viruses infecting them or them eating something with the viruses in it. But the kinds of viruses they spotted aren’t supposed to be able to infect protists — they infect bacteria.

And the researchers didn’t consistently find signs of those bacteria. So, it didn’t seem like a turducken situation, either — which left them with the conclusion that the viruses were the intended meal. This all matters because we don’t really know how viruses fit into food webs.

And mapping out who eats who is essential for understanding how nutrients move around and predicting how ecosystems might respond to environmental changes, like from climate change. Who knows—we may even be able to capitalize on the abilities of virus-eaters, like to help manage water quality. And if nothing else, since it’s unlikely we’ll become big fans of viruses overall, it’s perhaps just nice to know something is munching on them.

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So it’s 20% cheaper for you to wrap your brain around the science of infinity, or brush up on the fundamentals of chemistry. You can head over to Brilliant.org/SciShow to learn more. [♪ OUTRO].