Ancient Giant Viruses Revived After 30,000 Years In Siberian Permafrost

Image courtesy of Julia Bartoli and Chantal Abergel, IGS and CNRS-AMU.An ultrathin section of a Pithovirus particle in an infected Acanthamoeba castellanii cell observed by transmission electron microscopy. The length of the particle is ~1.5 µm with a 0.5 µm diameter.

It's not so often that new viruses are discovered on Earth, and it's even less frequent that researchers revive a 30,000-year-old virus from the Siberian permafrost - but that's just the kind of out-there stuff that researchers just did and published in the journal PNAS.

The virus they found frozen in the ice is related to modern viruses. It seems to be part of a group of "giant viruses" that researchers have been exploring since they were first discovered a decade ago.

Luckily, this newfound virus isn't known to infect humans at all.

These resurrected giant viruses from the ice core were revived in the lab, after researchers first melted the permafrost samples, then exposed a tiny animal called a protozoan to the resulting water. This specific protozoan was one they knew is frequently infected by these giant viruses.

After exposure to the water, the researchers discovered that the protozoan was infected with a previously unknown virus that seemed very similar to the two types of giant viruses we've found alive today, but that they have never seen before.

They named it Pithovirus sibericum, and it's one of the biggest giant viruses that researchers have ever found - measuring in at 1.5 micrometers long. That's about the same size as a small bacteria.

They found three very fascinating, surprising, and confusing things:

• The new giant virus expresses the same kinds of proteins as the giant virus type known as Megaviridae.
• However, it has the same shape to the a smaller type of giant virus, known as Pandoravirus.
• Even stranger, its genome is very different and much smaller than both of these other giant viruses.

These findings are super confusing (but also exciting!) to researchers who found the virus, evolutionary biologists Jean-Michel Claverie and Chantal Abergel, a husband-and-wife research team at Aix-Marseille University in France. One of them told Ed Yong, writing for Nature News: "We don't understand anything anymore!"

While this virus is completely benign, it's completely possible that other ancient viruses could be freed from the Arctic's frozen clutches as the climate warms the area and mining disrupts it, causing permafrost melt and turnover, the researchers said.

While that sounds terrifying and like a great plot for a Stephen King book, here's a note of caution from Curtis Suttle, a virologist at the University of British Columbia who was not involved in the work, as written by Yong:

People already inhale thousands of viruses every day, and swallow billions whenever they swim in the sea. The idea that melting ice would release harmful viruses, and that those viruses would circulate extensively enough to affect human health, "stretches scientific rationality to the breaking point," he says. "I would be much more concerned about the hundreds of millions of people who will be displaced by rising sea levels."

Here's another picture of the giant virus:

Image courtesy of Julia Bartoli and Chantal Abergel, IGS and CNRS-AMU.An ultrathin section of a Pithovirus particle in an infected Acanthamoeba castellanii cell observed by transmission electron microscopy. The length of the particle is ~1.5 µm with a 0.5 µm diameter.