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FFT
Emperor of the Galaxy
Joined: 26 Mar 2005
Posts: 5907
Location: Memphis
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 Posted: Wed Jun 11, 2008 5:36 pm Post subject: Bacterial metabolism evolution observed |
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| Quote: | 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.
Twenty years ago, evolutionary biologist Richard Lenski of Michigan State University in East Lansing, US, took a single Escherichia coli bacterium and used its descendants to found 12 laboratory populations.
The 12 have been growing ever since, gradually accumulating mutations and evolving for more than 44,000 generations, while Lenski watches what happens.
Profound change
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.
Indeed, the inability to use citrate is one of the traits by which bacteriologists distinguish E. coli from other species. The citrate-using mutants increased in population size and diversity.
"It's the most profound change we have seen during the experiment. This was clearly something quite different for them, and it's outside what was normally considered the bounds of E. coli as a species, which makes it especially interesting," says Lenski.
Rare mutation?
By this time, Lenski calculated, enough bacterial cells had lived and died that all simple mutations must already have occurred several times over.
That meant the "citrate-plus" trait must have been something special – either it was a single mutation of an unusually improbable sort, a rare chromosome inversion, say, or else gaining the ability to use citrate required the accumulation of several mutations in sequence.
To find out which, Lenski turned to his freezer, where he had saved samples of each population every 500 generations. These allowed him to replay history from any starting point he chose, by reviving the bacteria and letting evolution "replay" again.
Would the same population evolve Cit+ again, he wondered, or would any of the 12 be equally likely to hit the jackpot?
Evidence of evolution
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.
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.
In the meantime, the experiment stands as proof that evolution does not always lead to the best possible outcome. Instead, a chance event can sometimes open evolutionary doors for one population that remain forever closed to other populations with different histories.
Lenski's experiment is also yet another poke in the eye for anti-evolutionists, notes Jerry Coyne, an evolutionary biologist at the University of Chicago. "The thing I like most is it says you can get these complex traits evolving by a combination of unlikely events," he says. "That's just what creationists say can't happen."
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0803151105) |
Last edited by FFT on Wed Jun 11, 2008 10:15 pm; edited 1 time in total |
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admin
Beloved Admin
Joined: 28 Sep 2000
Posts: 1696
Location: Macau, China
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| Posted: Wed Jun 11, 2008 8:02 pm Post subject: |
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Lies, lies and more lies. You evolutionists are thinking and learning all the time. Please stop.
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RevJP
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Posts: 6845
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| Posted: Thu Jun 12, 2008 6:17 am Post subject: |
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I personally think this is exciting.
I can't wait to see when this bacterium evolves into something other than a bacterium... |
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45degreeN
King Kong
Joined: 02 Aug 2005
Posts: 2462
Location: Salem Oregon
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| Posted: Thu Jun 12, 2008 6:35 am Post subject: |
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Has there even been 20,000 generations of humans on this planet yet? Much less 31,500?
Bacterium can in fact generate these mutations simply because they live and die so fast that they can have that many generations in a reasonable human time frame and can be seen by humans studying them(virus' also.)
But what about larger species? |
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Ana
King of the Jungle
Joined: 10 Mar 2006
Posts: 1549
Location: BC
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| Posted: Thu Jun 12, 2008 7:51 am Post subject: |
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| RevJP wrote: |
I can't wait to see when this bacterium evolves into something other than a bacterium... |
That's probably true, as if it happens, it will probably be long after you're dead. |
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FFT
Emperor of the Galaxy
Joined: 26 Mar 2005
Posts: 5907
Location: Memphis
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| Posted: Thu Jun 12, 2008 12:33 pm Post subject: |
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| RevJP wrote: | I personally think this is exciting.
I can't wait to see when this bacterium evolves into something other than a bacterium... |
 And the award for completely not getting it goes to ... |
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FFT
Emperor of the Galaxy
Joined: 26 Mar 2005
Posts: 5907
Location: Memphis
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| Posted: Thu Jun 12, 2008 2:32 pm Post subject: |
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Apparently Behe wrote a blog about the article. Someone on another forum summed it up rather well:
His line of reasoning is essentially that this paper is bad news for evolution, because even a "simple" trait like the ability to metabolize citrate might require more than one mutation, which he finds improbable in spite of the fact that the paper demonstrated it happening. |
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RevJP
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Joined: 18 Apr 2003
Posts: 6845
Location: USA
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| Posted: Thu Jun 12, 2008 5:30 pm Post subject: |
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| Quote: | | And the award for completely not getting it goes to ... |
Oh, I got it completely. The paper demonstrated change.... yeah, so what? |
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FFT
Emperor of the Galaxy
Joined: 26 Mar 2005
Posts: 5907
Location: Memphis
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| Posted: Thu Jun 12, 2008 7:58 pm Post subject: |
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So what? This is the evolution of a new specie of bacteria (yes, they are still bacteria and no, pointing this out is not brilliant). And not only that, it's reproducible.
It's evolution at work. |
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Dust
Growing Lion
Joined: 10 Sep 2004
Posts: 883
Location: All over the western U.S.
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| Posted: Thu Jun 12, 2008 9:05 pm Post subject: |
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Hmm.......A mere play on words FFT.
I contend that your accepted definition of "new specie" is skewed.......and furthermore, as it pertains to your application.....PURPOSELY misleading. |
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FFT
Emperor of the Galaxy
Joined: 26 Mar 2005
Posts: 5907
Location: Memphis
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| Posted: Fri Jun 13, 2008 12:52 am Post subject: |
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| Define how you want "Specie" to be used, then. |
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RevJP
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| Posted: Fri Jun 13, 2008 6:44 am Post subject: |
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Didn't we do this 'definition' game already.
bacterium = bacterium, fruit fly = fruit fly, evolution = change...
How exactly does this get us from bacterium to goat, andif it doesn't, then who cares? |
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Ana
King of the Jungle
Joined: 10 Mar 2006
Posts: 1549
Location: BC
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| Posted: Fri Jun 13, 2008 8:42 am Post subject: |
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| RevJP wrote: | | Quote: | | And the award for completely not getting it goes to ... |
Oh, I got it completely. The paper demonstrated change.... yeah, so what? |
| RevJP wrote: | Didn't we do this 'definition' game already.
bacterium = bacterium, fruit fly = fruit fly, evolution = change...
How exactly does this get us from bacterium to goat, andif it doesn't, then who cares? |
The coloured parts above are my highlights. Substitute red into blue and we get:
The paper demonstrated evolution.
And this is all according to you. Congratulations!  |
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RevJP
Moderator
Joined: 18 Apr 2003
Posts: 6845
Location: USA
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| Posted: Fri Jun 13, 2008 10:41 pm Post subject: |
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Congratulations for what? That evolution means change and that any reasonable person understands that things change? 
What I'm still waiting for is that magic that somehow happens according to TOE proponents that one thing changes into some completely different thing. Thus far we have a bacterium changing into a mutated bacterium, and we have genetically manipulated fruit flies changing into mutated fruit flies...
Admittedly I've glossed over the 'magic' portion as defined by TOE proponents = incalculable amounts of time.... |
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FFT
Emperor of the Galaxy
Joined: 26 Mar 2005
Posts: 5907
Location: Memphis
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| Posted: Fri Jun 13, 2008 10:56 pm Post subject: |
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It's an entirely novel specie of bacteria that evolved from E. coli. 20 years and a miniscule population relative to bacteria in the wild. The specie developed due to multiple neutral mutations stacking up over time. And not only that, it's more successful than E. coli. It's exactly the sort of thing that ID proponents say can't happen. Of course, the refrain will go back to "but it's still a bacteria "
No one that actually understands the theory of evolution expects to see bacteria evolve into something other than bacteria. No one that actually understands the theory of evolution expects to see "one thing change into some completely different thing" as you seem to define it. |
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