You just sat down to dinner, and in addition to that lovely plate of food in front of you, there’s a glass of wine, as well. While that wine makes everything a little more pleasurable, what your body needs is the food and it could get by without the wine at all. Trying to flip that that equation around and surviving on alcohol would put you in a very sorry state: constantly drunk, and beset by rickets, scurvy, and other metabolic deficiencies.
Now imagine a genetic mutation, that allows you not only to live on alcohol, but you actually survive better on it than you do on normal food, sort of like the character Bender in Futurama. Something almost like this has happened to a strain of E. coli bacteria that have been living in a Michigan laboratory for the past 25 years.
These bacteria normally feed on glucose, a sugar, which is stabilized in solution by sodium citrate. Sodium citrate is not a chemical that E. coli can typically metabolize. In Richard Lenski‘s lab, however, one strain has evolved to eat the citrate, not the glucose.
Lenski and his team have raised 55,000 generations of E. coli, the equivalent in human terms, of over a million years of evolution. Because Lenski deep freezes a few specimens every 500 generations, he is able to track the genetic changes in the bacteria over time with DNA sequencing.
Sometime around generation 20,000 a mutation (or set of mutations) occurred, it had no particular negative nor positive benefit, and was carried by successive generations. Then, 11,000 generations later, another mutation gave beneficial properties to the first mutation. Only after the second mutation could the bacteria metabolize the citrate at all. Within a few hundred more generations, however, the E. coli mutated even further to maximize that small benefit, and are now thriving on the citrate.
Carl Zimmer, one of my favorite science writers, describes this evolutionary process in much more detail, and also notes that this is essentially the same mechanism that turned a pancreatic enzyme into snake venom.
Suppose you were an idiot. And suppose you were a member of Congress. But I repeat myself. — Mark Twain
I originally started this post as pure science geekery. However, I learned yesterday that Congresscritter Paul Broun, who remarkably, has both an M.D. and a chemistry degree, is telling his constituents that “evolution…all that is lies.” Now I tend to just roll my eyes at the lunatic fringe of politics, but Broun is on the House Science Committee, which oversees all non-defense related science research.
Like the cardinals who refused to look through Galileo’s telescope, Braun is choosing willful ignorance over facts in plain view. I’d like to quote Bender and tell Paul Broun and those who appointed him to that position to “Bite my shiny metal ass.”