This article was originally posted on RealClearScience.
As a general rule-of-thumb, eukaryotic cells (e.g., amoebae or human body cells) are about 1,000 times bigger than bacteria, and bacteria are about 10-100 times bigger than viruses. But in biology, there is rarely such a thing as an inviolable rule. For example, two types of giant amoeba-infecting viruses, known as Megaviridae and Pandoravirus, are so large that they are comparable to bacteria in terms of physical size and genome length.
Now, after poking around in the Siberian permafrost, a team of French and Russian scientists have reported the discovery of a third. The virus, which they named Pithovirus, resembles a mishmash of the two previously known giant viruses. And remarkably, it is 30,000 years old!