"Bacteria make major two step evolutionary nutritional shift in the lab."

From New Scientist

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But sometime around the 31,500th generation, something dramatic happened in just one of the populations - the bacteria suddenly acquired the ability to metabolise citrate, a second nutrient in their culture medium that E. coli normally cannot use.

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The replays showed that even when he looked at trillions of cells, only the original population re-evolved Cit+ - and only when he started the replay from generation 20,000 or greater. Something, he concluded, must have happened around generation 20,000 that laid the groundwork for Cit+ to later evolve.

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Lenski and his colleagues are now working to identify just what that earlier change was, and how it made the Cit+ mutation possible more than 10,000 generations later.

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It'll be interesting to keep an eye on this, and see exactly what happened at the two points of change.Edited by bluegenes, : Title change from original NS article title for fussy admin!

Would you please edit it to something that more specifically reflects message 1's content?No replies to this message.AdminnemooseusNote: Original title is/was "Bacteria make major evolutionary shift in the lab."

Bump for Jazzns.Already here, but it would be good to have a discussion on this.Edited by bluegenes, : title

I like the wiki treatment of this that I put into my failed new thread.E. coli long-term evolution experiment - WikipediaI was under the impression from reading this that what evolved is actually IC. Of course the article is not discussing IC because its not really an issue for these folks. Its not like they were doing these expirments to prove that IC systems can evolve. Obviously they did in fact evolve and this just seems to be an example where we have watched it do so.I guess I thought about the connection to IC because of that 2-step process that kicked off the change. It took 2 changes to get allow the bacteria to absorb the new nutrient and a further one enhanced their ability to utilize it.

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Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget)

And: Exactly. In this little village. But I tried! Just that! Did you start working out the statistics in your head of what that means in the wild?--------------------------------------------------------------------------------

Not sure what you mean by this.What really drew me in was the description of the first mutation. It is exactly the process that is often described but so many anti-evos just don't get. The first one was just a product of drift, a neutral mutation that essentially did nothing.It was when it was finally paired with the 2nd mutation that finally allowed the cell to absorb the new nutrient. In fact, since they were able to rewind the clock based on the frozen shapshots, none of the lines before drift were likely to reevolve the feature but those after were.I would have though that this would have at least illicited a "but its still a bacteria" response from someone.

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Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget)

It did. Even hilarious "this proves our point about change within kinds".What I meant was that what does 20 years or 40,000 generations mean in the wild? What happened yesterday in your toilet?The rest of your post is just that. A little "I.C." mechanism comes easily. Historical contingency must be an every day fact.

There is absolutely no evidence for this. The original paper itself says in its discussion ... Without an answer to this question we can't say if this is an example of an IC feature.TTFN,WK

True. But as I understood it, they didn't notice the first mutation, but only discovered it in retrospect. Wouldn't that indicate either no advantage or only a very slight advantage?

It only really indicates that it was not as drastically an advantageous a mutation as being able to utilise a whole new food source, which is pretty radical.TTFN,WK

If it was a mutation that conferred some kind of general advantage that didn't relate to the food source, wouldn't it already exist in the wild? It would seem to me that in order to be selected for, it would have to relate to the specific circumstances that Lenski was keeping the bacteria in.Wouldn't it be statistically extremely unlikely that any of Lenski's bacteria hit on a mutation that is of general advantage to the species in such a short time (relatively speaking)?

Either way, I think it's just as IC as anything Behe's come up with.On the face of it, it's a two-part system, and without either part it can't metabolise citrate.But I'll await further research.

Yes, look at it that way, and it's IC by Behe's own definition. It could even turn out to be three part system.Wounded King might be able to give us a guesstimate as to how long it might take Lenski and his colleagues to identify the mutations and figure out how the system works.

Well, one of the more minor problems with Behe's ideas it that we don't know how to count "parts".Take my head as one part and the rest of me as another, and I'm IC. Then, of course, we point out all the organisms that get along fine without heads, and explain the theory of evolution for the zillionth time ...

Who says it doesn't? It would have to confer a benefit in those circumstances but there is no reason it need confer a benefit only in those circumstances. I don't see why. Lenski claims that the population size, generation numbers, and mutation rate are such that any possible single step point mutation should have occurred at some point. It seems unlikely that none of these might have generally beneficial effects. Having said that the paper suggests that a single point mutation is an unlikely candidate for the predisposing mutation. They seem to have some reasonable candidates for what might be the physiological mechanism allowing the aerobic citrate transport so finding one of the mutations might not be so hard. The main problem is that so far the only phenotypic effect associated with the potentiating mutation is its potentiating effect. I don't know how extensive the genetic variation is in their frozen down stock populations but I think it could be a pretty exhausting task to try and track down unique differences between the populations before and after the potentiating mutation occurred.So really I don't have a best guess, sorry.TTFN,WK