I’m glad the Large Hadron Collider is getting so much press; it’s a rare day that physics takes center stage in the minds of everyday people. Searching for fundamental unifying forces of the universe by smashing atomic particles at near-light speed into each other inside the largest machine ever constructed by human beings is pretty damn awesome. The cutting-edge discoveries that come from it (or the ones that conspicuously fail to) will undoubtedly play a large role in our understanding of the most illusive workings of the universe. So you might be surprised to know that I find research that began 20 years ago with some bacteria in a jar to be even more exciting.
Richard Lenski’s research at Michigan State University is breathtaking. The procedure is stupefyingly simple but the results are stunningly elegant. Not only has he observed evolution in a laboratory setting, but he’s provided snapshots of every step along the way. And when a novel ability was eventually coughed up by natural selection, he rebooted from past generations to see exactly where and how it happened.
It all went a little something like this:
In 1988 Lenski and his team started out with a single microbe of E. Coli, allowed it to divide, and from its offspring he started 12 colonies. They were kept in separate containers, each filled with a glucose-citrate solution. Every day, samples from each colony were frozen and the solution replenished. (E. Coli feed on glucose, but it is an identifying attribute of the bacteria that they can not consume citrate because they are unable to pull it through their membranes.) This process provides a record of genetic change every 500 or so generations that can be resurrected and compared to bacteria at any other stage.
From Carl Zimmer’s article A New Step in Evolution:
Over the generations, in fits and starts, the bacteria did indeed evolve into faster breeders. The bacteria in the flasks today breed 75% faster on average than their original ancestor. Lenski and his colleagues have pinpointed some of the genes that have evolved along the way; in some cases, for example, the same gene has changed in almost every line, but it has mutated in a different spot in each case. Lenski and his colleagues have also shown how natural selection has demanded trade-offs from the bacteria; while they grow faster on a meager diet of glucose, they’ve gotten worse at feeding on some other kinds of sugars.
But then… after 33,127 something weird was going on.