Lenski’s Lab: The Gift that Keeps on Giving
About 23 years ago, a researcher by the name of Richard Lenski started a long term experiment. It’s still running.
He started with Escherichia coli, a common bacteria in the human intestinal system, though wild versions can cause disease. Every single day, for 23 years, he or one of his lab assistants has extracted E. coli from the flasks in which they are living and placed them into fresh flasks with just a nutrient solution. Every 75 days, or 500 bacteria generations, they deep freeze a population sample from every lineage. They can literally trace the lineage of every single bacterium in their lab.
Not too long ago, they reported something amazing. One of the defining characteristics of E. coli is that the bacteria cannot metabolize citrate. This is so well known and understood that it is used as a test to see if a bacterium is E. coli or Enterobacter aerogenes (for example, which is a soil bacterium). However, when Lenski looked at one of his flasks, which uses citrate in the medium, he saw it was cloudier than normal.
In fact, at about 31,500 generations, one of the populations of E. coli had evolved the ability to metabolize citrate. Now, that’s very cool for 2008, but what have you done for me lately?
Oh, it gets better. Remember that they freeze the bacteria every 500 generations. So, one of Lenski’s people, started going back and taking some of the old populations and starting them growing again. They found that several populations after generation 20,000 eventually evolved the citrate metabolizing trait. However, no population prior to generation 20k evolved the citrate trait. So, sometime about generation 20k, something happened… something wonderful (bonus points if you can identify the quote).
Again, this was several years ago, so again, I ask, what have you done for me lately?
Enter the latest study from Lenski’s lab. Pretty soon, they’re just going to make a peer-reviewed journal for lab’s work. I need to e-mail Lenski and see if I can get a copy of his report… Nature is rather expensive for a lone blogger (if anyone would like to donate, that would be awesome).
Anyway, remember those frozen samples? Well, they broke those out again… and sequenced the genomes.
What they found was several potentiating mutations. Only the populations whose ancestors had those mutations (two of them) would become citrate users.
The next stage was actualization, that is, the bacteria first became able to utilize citrate. It wasn’t a lot and it wasn’t very efficient. But those particular bacteria had an epic advantage over any other in their culture. They could use a source of energy that none of their competitors could use. The population exploded, resulting in the cloudiness of the flask.
During this stage, a mutation occurred. This wasn’t a simple point mutation, like what occurs to generate sickle cell anemia. This was a complex mutation that literally rearranged a part of the bacterial genome. Part of the genome was copied and two sequences of DNA were linked together in a new way. This change created a new TWO-PART biochemical pathway that allowed citrate to get into the bacterium and then to allow the citrate to be chemically metabolized.
This new protein pathway has never existed before and may never occur in any E. coli population again. It’s a combination of improbable chances. But it happened. This is a stunning result.
One reason that it is so stunning is that is completely blows an entire massive chunk of the Intelligent Design argument into the trash bin. The IDists (I’m to polite to use IDiot here), keep saying that the changes that Lenski’s group describes can’t happen. Evolution can’t develop multiple mutations that don’t do anything, but eventually turn into something useful. Evolution can’t develop an entirely new multiple protein pathway. Evolution can’t… can’t… can’t…
Oh wait. It can. It did. It’s right there. A complex genome rearrangement resulting in two new proteins that create a new multi-protein regulatory module that never existed before.
Now, since this has indeed occurred. It’s a perfect opportunity for the IDists. This is the thing that they should have been waiting for with baited breath. This is the one.
Lenski’s lab has detailed sequences. They know, to within 75 days, when all these mutations occurred. They know what sequences where changed. They have frozen samples that show all this.
All the IDists have to do is find the evidence that a designer purposefully manipulated the genome. If it happened, then it’s in that data, in those organisms, somewhere. Get to work IDists. I won’t hold my breath though.
UPDATE: Dr. Blout has responded and sent me a copy of the paper and Southstar has posted a link: http://bms.ucsf.edu/sites/ucsf-bms.ixm.ca/files/20121011.strauli.nicolas.pdf