Bacteria make major evolutionary shift in the lab

[daniel_i_l]

I recently came across this article:
http://www.newscientist.com/article/dn14094-bacteria-make-major-evolutionary-shift-in-the-lab.html

A major evolutionary innovation has unfurled right in front of researchers' eyes. It's the first time evolution has been caught in the act of making such a rare and complex new trait.

And because the species in question is a bacterium, scientists have been able to replay history to show how this evolutionary novelty grew from the accumulation of unpredictable, chance events.
...

Mostly, the patterns Lenski saw were similar in each separate population. All 12 evolved larger cells, for example, as well as faster growth rates on the glucose they were fed, and lower peak population densities.

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.

Has anything on this scale ever been observed before?
Lenski's freezer must be an immensely valuable source of evolutionary information.
And one question, why is "lower peak population densities" something E. coli would evolve towards. Wouldn't the more successful ones have a higher population density?

 

[Pattonias]

Wouldn't they have to recreate the phenomenon before they could say the experiment "proves" anything?

On the other hand, is this different than a bacteria/virus gaining a resistance to a drug? Isn't that a commonly occurring form of evolution along the same lines?

 

[arildno]

Wouldn't they have to recreate the phenomenon before they could say the experiment "proves" anything?

On the other hand, is this different than a bacteria/virus gaining a resistance to a drug? Isn't that a commonly occurring form of evolution along the same lines?

Not really.

Most of the immune-resistency comes out of normally "failed" bacteria, i.e, where that structure the anti-biotic targets works IMPROPERLY (thus, the anti-biotic fails to hook onto that defective structure).

I.e, these mutants would in a non-anti-biotic setting have lower reproduction rates etc than the standard strand, and be quickly swamped/smothered.


In this case, however, a strictly beneficial trait is seen to emerge, rather than a trait which is onnly beneficial in a much more specialized setting (i.e, the anti-biotic environment)

 

[ideasrule]

More detailed article: http://en.wikipedia.org/wiki/E._coli_long-term_evolution_experiment

Interestingly, 4 out of the 12 samples actually evolved a higher mutation rate, perhaps because a higher mutation rate was actually beneficial.

 

[Sorry!]

I think these experiments are old...

 

[arildno]

I think these experiments are old...

Well, if they have established that gen 20.000 could give rise to citrate-utilizing gen 32.000, then clearly, the initial observation of citrate-utilization happened well over 10.000 generations ago.

 

[russ_watters]

Wouldn't they have to recreate the phenomenon before they could say the experiment "proves" anything?

No: evolution does not claim to be a linear process.