Innovation

Study shows how swiftly infectious viruses evolve

When a virus can't infect its target cell, how long does it take for it to evolve to successfully invade it again? A new study has a frightening answer.

Written by Laura Shin, Contributor Jan. 30, 2012 at 9:40 p.m. PT

When viruses face an obstacle to infecting the cells they normally infect, how long does it take for them to evolve to successfully invade them again? A new study has a frightening answer: just a little more than two weeks.

The study raises more questions and fears about the evolution of viruses just a month after the government asked two scientific journals to halt publication of details about bird flu viruses that were cultivated in the lab to be easily transmitted among humans.

In this latest study, published Thursday in the journal Science, a team of scientists at Michigan State University studied a virus that is harmless to humans, called lambda, which normally infects the bacterium, Escherichia coli.

Normally, lambda gets into E. coli by latching onto a molecule on the bacterium's surface. From there, it injects its won genes and proteins in the microbe.

Justin Meyer, a graduate student in the biology laboratory of Richard Lenski, created a version of E. coli that had almost none of the molecules lambda needs to infect the bacterium, so that very few of the lambda cells could get in.

But within 15 days, the lambda cells had evolved to use a different molecule, called OmpF, to invade E. coli. As the New York Times reports, "Lambda viruses had never been reported to use OmpF before. Mr. Meyer was surprised not just by how fast the change happened, but that it happened at all. “I thought it would be a wild goose chase,” he said. "

To see if the rapid evolution was just an aberration, he did the same test with 96 lines. In 24 of the lines, not only did the viruses all mutated to use OmpF, but they all did so in a series of four mutations. On top of that, in almost all of them, the four mutations were identical.

The Times says,

Some critics have argued that full-blown evolution would not be able to mimic the highly artificial Dutch experiment. The chances that a single virus would acquire so many mutations at once are certainly small. In the case of lambda viruses, Mr. Meyer estimates the chance of all four mutations arising at once is roughly one in a thousand trillion trillion.

Additionally, the virus did not succeed in developing the proper mutation in the majority of cases. Why? As MSNBC reports, the bacteria also mutated, producing a protein on the inner membrane that prevented the virus from entering the cell.

The study shows the potential for us to predict the evolution of viruses and bacteria, plus gives us new insight into how viruses that attack humans, such as the deadly bird flu virus, might evolve.

Watch this video about the study on the lambda virus: