Study Finds Virus to Be Fast Learner on Infecting

Viruses regularly evolve new ways of making people sick, but scientists usually do not
become aware of these new strategies until years or centuries after they have evolved. (…)
However, a team of scientists at Michigan State University describes how viruses evolved a new
way of infecting cells in little more than two weeks. (…)
5 The Michigan researchers studied a virus known as lambda. It is harmless to humans, infecting only
the gut bacterium Escherichia coli. Justin Meyer, a graduate student in the biology laboratory of
Richard Lenski, wondered whether lambda might be able to evolve an entirely new way of getting
into its host. The standard way for lambda to get into a cell is to latch onto its outer membrane,
attaching to a particular kind of molecule on the surface of E. coli. It can then inject its genes and
10 proteins into the microbe. Mr. Meyer set up an experiment in which E. coli made almost none of the
molecules that the virus grabs onto. Now few of the viruses could get into the bacteria. Any
mutations that allowed a virus to use a different surface molecule to get in would make it much
more successful than its fellow viruses. (…) 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
15 been reported to use OmpF before. Mr. Meyer was surprised not just by how fast the change
happened, but that it happened at all.
To see if this result was just a fluke1, Mr. Meyer ran his experiment again, this time with 96 separate
lines. The viruses in 24 of the lines evolved to use OmpF. The researchers sequenced the genomes
of the evolved viruses and were surprised to find that this transformation always required four
20 mutations. In all the lines that could grab OmpF, those four mutations were identical, or nearly so.
No single mutation could allow the viruses to start latching onto OmpF. Even three out of four
mutations brought no change. Only after they developed all four mutations could the viruses make
the switch.
(…) The new experiment provides a surprising glimpse at how easily viruses can evolve entirely
25 new traits through new mutations — and thus give rise to new diseases.
By CARL ZIMMER, January 26, 2012 The New York Times
Sum up this article and explain the main ideas using your scientific knowledge
1 fluke = an accidental stroke of luck