NY Times link
In the corner of a laboratory at Michigan State University, one of the longest-running experiments in evolution is quietly unfolding. A dozen flasks of sugary broth swirl on a gently rocking table. Each is home to hundreds of millions of Escherichia coli, the common gut microbe. These 12 lines of bacteria have been reproducing since 1989, when the biologist Richard E. Lenski bred them from a single E. coli. “I originally thought it might go a couple thousand generations, but it’s kept going and stayed interesting,” Dr. Lenski said. He is up to 40,000 generations now, and counting.
One such study is of Myxococcus xanthus, (photo) which lash their tails together and hunt in a pack. If they starve, they form a ball, above.
In that time, the bacteria have changed significantly. For one thing, they are bigger — twice as big on average as their common ancestor. They are also far better at reproducing in these flasks, dividing 70 percent faster than their ancestor. These changes have emerged through spontaneous mutations and natural selection, and Dr. Lenski and his colleagues have been able to watch them unfold.
When Dr. Lenski began his experiment 18 years ago, only a few scientists believed they could observe evolution so closely. Today evolutionary experiments on microbes are under way in many laboratories. And thanks to the falling price of genome-sequencing technology, scientists can now zero in on the precise genetic changes that unfold during evolution, a power previous generations of researchers only dreamed of.