How Giant Viruses Work

The discovery of giant viruses is changing the face of virology.
The discovery of giant viruses is changing the face of virology.
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I only like the word "giant" relative to fun stuff, like beers and brownies. Viruses I prefer to be tiny and easily overcome, if not completely absent from my life. So it's easy to see why the ever-increasing publicity of "giant viruses" is whipping people into a complete frenzy. Before we resort to living in plastic bubbles, though, it's important to understand the basics of giant viruses and what types of risks they might or might not pose.

To draw an accurate picture, it helps to know what a so-called "standard" virus looks like. "Typically, we think of a virus as having a handful of genes, making a few proteins to replicate themselves," explains Steven W. Wilhelm, Ph.D., graduate director and associate head of the department of microbiology at The University of Tennessee. "These giant viruses are a bit of a different story in that they contain dozens or hundreds of genes."

According to Wilhelm, giant viruses are still so new that they lack hard-and-fast criteria. However, the most basic rule of thumb is that these viruses have genomes that total more than a quarter million base pairs in size. "The genome is kind of the blueprint of the cell, and the base pairs are the components that make up that blueprint," he says.

Even if you don't fully grasp what that means, this comparison will bring home the difference between a normal virus and a giant version. Take, for instance, the human immunodeficiency virus (HIV), which is probably the most studied virus in the world. HIV sports 9,749 base pairs. By contrast, the largest giant virus currently known is Pandoravirus, which boasts 2 million base pairs, according to Wilhelm. Pandoravirus also has DNA that dwarfs regular viruses, with 2,500 genes versus the standard 10 found in most smaller versions. It also far outsizes other viruses at 1 micron in length (a thousandth of a millimeter), as opposed to normal viruses that range between 50 and 100 nanometers (there are 1,000 nanometers in a micron) [source: Dell'Amore].

In essence, we're talking about regular viruses gone Hulk, albeit on a microscopic level. So is it time to freak out, or should we take a wait-and-see approach?