Pandoraviruses

This is a truly amazing discovery, and it may turn out to be one of the most important biological discoveries in decades:

The organism was initially called NLF, for “new life form”. Jean-Michel Claverie and Chantal Abergel, evolutionary biologists at Aix-Marseille University in France, found it in a water sample collected off the coast of Chile, where it seemed to be infecting and killing amoebae. Under a microscope, it appeared as a large, dark spot, about the size of a small bacterial cell.

Later, after the researchers discovered a similar organism in a pond in Australia, they realized that both are viruses — the largest yet found. Each is around 1 micrometre long and 0.5 micrometres across, and their respective genomes top out at 1.9 million and 2.5 million bases — making the viruses larger than many bacteria and even some eukaryotic cells.

But these viruses, described today in Science, are more than mere record-breakers — they also hint at unknown parts of the tree of life. Just 7% of their genes match those in existing databases. “What the hell is going on with the other genes?” asks Claverie. “This opens a Pandora’s box. What kinds of discoveries are going to come from studying the contents?”

Claveria and Abergel believe that these giant viruses evolved from cells, and they hope to show by studying the viral DNA what sort of cells those were. They may prove to be something as yet unknown, a form of life neither bacteria, archaea, nor eukaryote:

“We think that at some point, the dynasty on Earth was much bigger than those three domains,” says Abergel. Some cells gave rise to modern life, and others survived by parasitizing them and evolving into viruses.

Like astronomers minutely examining the microwave background radiation for clues about the Big Bang, evolutionary biologists are always hoping for evidence of what life on earth was like in the first billion years, before it evolved into the kinds we know. These giant viruses might provide a clue.

But even if that can't be sorted out, or they descend from bacteria, they are still GIANT VIRUSES, a whole new domain of life. What an incredible place the world is.