A new study published in Science shows how quickly viruses evolve new infection strategies, says The New York Times' Carl Zimmer. Researchers at Michigan State University say they observed viruses working out a new strategy in little more than two weeks.
The Science study focused on lambda virus, which infects E. coli. The virus usually clamps on to a specific molecule on the cell's outer membrane and then injects its genes and proteins into its host, Zimmer says. The researchers created an experiment in which the E. coli hosts had almost none of the molecule the virus needs to see how the virus might mutate to overcome the difficulty. "The scientists found that in just 15 days, there were viruses using a new molecule — a channel in E. coli known as OmpF. Lambda viruses had never been reported to use OmpF before," Zimmer says. "The researchers sequenced the genomes of the evolved viruses and were surprised to find that this transformation always required four mutations. In all the lines that could grab OmpF, those four mutations were identical, or nearly so."
The researchers estimate that the chances of all four mutations arising at once in lambda are about one in a thousand trillion trillion, Zimmer adds. But experts say that such studies show that researchers may at some point be able to forecast the evolution of viruses and bacteria.