Epilogue

The Alien in the Watercooler

Mimivirus

Wherever there is water on Earth, there is life. The water may be a pond in a tropical forest, a
pool in the Cave of Crystals, or a cooling tower sitting on the roof of a hospital.

In 1992, a microbiologist named Timothy Rowbotham scooped up some water from a hospital
cooling tower in the English city of Bradford. He put it under a microscope and saw a welter of life.
He saw amoebae and other single-celled protozoans, about the size of human cells. He saw bacteria,
about a hundred times smaller. Rowbotham was searching for the cause of an outbreak of pneumonia
that had been raging through Bradford. In the ranks of the microbes he found in the cooling tower
water, he thought he found a promising candidate: a sphere of bacterial size, sitting inside an amoeba.
Rowbotham believed he had found a new bacterium, and dubbed it Bradfordcoccus.

Rowbotham spent years trying to make sense of Bradfordcoccus, to see if it was the culprit in the
pneumonia outbreak. He tried to isolate its genes by searching for stretches of DNA found in all
bacteria, but he couldn’t find any. Budget cuts forced Rowbotham to close his lab down in 1998, and
so he arranged for French colleagues to store his samples. For five years, Bradfordcoccus languished
in obscurity, until Bernard La Scola of Mediterranean University, decided to take another look at it.
As soon as he put Rowbotham’s samples under a microscope, he realized something was not right.

Bradfordcoccus did not have the smooth surface of spherical bacteria. Instead, it was more like a
soccer ball, made up of many interlocking plates. And radiating out from its geometric shell La Scola
saw hairlike threads of protein. The only things in nature that have these kinds of shells and threads
were viruses. But La Scola knew, like all microbiologists at the time knew, that something the size of
Bradfordcoccus was a hundred times too big to be a virus.

Yet a virus is exactly what Bradfordcoccus turned out to be. La Scola and his colleagues
discovered that it reproduced by invading amoebae and forcing them to build new copies of itself.
Only viruses reproduce this way. La Scola and his colleagues gave Bradfordcoccus a new name to
reflect its viral nature. They called it a mimivirus, in honor of the virus’s ability to mimic bacteria.

The French scientists then set out to analyze the genes of the mimivirus. Rowbotham had tried—and
failed—to match its genes to those of bacteria. The French scientists had better luck. The mimivirus
had virus genes—and a lot of them. Before the discovery of mimiviruses, scientists were used to
finding only a few genes in a virus. But mimiviruses have 1,262 genes. It was as if someone took the
genomes of the flu, the cold, smallpox, and a hundred other viruses and stuffed them all into one
protein shell. The mimivirus even had more genes than some species of bacteria. In both its size and
its genes, mimivirus had broken cardinal rules for being a virus.

Once La Scola and his colleagues knew what mimivirus genes looked like, they began to search for
them in other habitats. They found the giant viruses in the lungs of hospital patients suffering from
pneumonia. It’s not clear yet if mimiviruses actually cause pneumonia, as Rowbotham had originally