Sunday, October 18, 2009

The Lenski Experiments



In the Lenski experiment the E.Coli cells grown in the presence of oxygen gained the ability to transport citrate across the membrane. The allowed them to utilize citrate as a carbon source and provided a selective advantage in the conditions of the experiment.

In the absence of oxygen with another suitable source of energy the E.coli cells are able to transport and use citrate.

The mutation(s) that occurred in the Lenski experiment therefore allowed (unusually) the transport of citrate across the membrane in the presence of oxygen.

As far as I am aware the detailed molecular story of what happened in this particular case has yet to be unravelled. It seems that at least two different mutations must occur for this ability to be conferred.

As far as I am aware no new proteins are involved. The most likely explanations are a loss of the usual control of the anaerobic citrate transport system or a mutation in a protein that transports a similar molecule

What is significant from these results is that even for this small modification in an existing protein 31,500 generations were required with a population size of about 5 million. This was in the presence of the heaviest selection pressure possible.

Behe argues that this work is consistent with his arguments regarding the limit of evolution.

Behe’s discussion of the Lenski work.

A recent Scientific American article on the Lenski experiment. (HT to Psilo)

22 Comments:

Blogger Psiloiordinary said...

The genetics has been done Andrew!

A new adaptation relying on more than one mutation? I thought that was supposed to be impossible? New information and an irreducibly complex adaptation?

Your move.

Regards,

Psi

PS why not go for the "but they are still bacteria!" move?

;-)

7:35 am  
Blogger Psiloiordinary said...

Hi Andrew,

I tried to post this already;

The genetics has been done - read the work - not Behe's silly claims about it.

This is also what you have previously called irreducibly complex; i.e. the various mutations don't work until they are combined.

Any response?

Regards,

Psi

5:10 pm  
Blogger Andrew Rowell said...

Psi,

We are talking at cross purposes.
I am not talking about one or two or several mutations altering the function of a protein.

I am talking about the creation of an entirely new protein as the very first representative of an entirely new family of proteins with no homologues.

I read the work and it is nothing to do with what I was talking about. I was impressed with how closely however it matches Behe's ideas in "The Edge."

I was impressed with how many generations with the most intense selection pressure are required for a relatively trivial change.

Lenski specifically states that there are no claims of any new proteins in his work.

6:04 pm  
Blogger Psiloiordinary said...

So why are you are talking about abiogenesis as if it has something to do with evolution?

10:01 pm  
Blogger Andrew Rowell said...

Psi,

It is true that abiogenesis requires a large number of new proteins all at once. However that was not what I was talking about here. I am thinking of large steps in evolution which require a totally new protein which has no significant sequence homology to other known proteins.

As complexity increases in living things the number of proteins required increase. Many of these have no sequence homology with each other. Evolution requires that these brand new proteins appear without any intelligent input.

10:27 pm  
Blogger Psiloiordinary said...

Andrew,

Have you seen the episode of Only fools and horse were trigger has been working as a street sweeper for a large number of years and he announces he has been using the same brush all that time.

He later confirms that he has changed the handle several times, and the bristles several times.

Get it?

Psi

PS

Do you now accept Lenski has observed Irreducible Complexity occurring?

8:01 am  
Blogger Andrew Rowell said...

No, No and No.

8:17 am  
Blogger Psiloiordinary said...

Hi Andrew,

Ok so what was your definition of irreducible complexity again?

Please spell it out in your own words and we can compare it with what Lenski saw.

- - -

Re "large steps in evolution" here are a few examples of what you claim doesn't exist;

Ganfornina M. D., Sanchez D. 1999. "Generation of evolutionary novelty by functional shift." Bioessays. 21(5):432-9.

Mayr, E. 1960. "The Emergence of Evolutionary Novelties." in Evolution After Darwin: Volume 1: The Evolution of Life: Its Origin, History, and Future, Sol Tax, ed. The University of Chicago Press, Chicago, IL. pp. 349-380.

Pellmyr, O. and Krenn, H. W., 2002. "Origin of a complex key innovation in an obligate insect-plant mutualism." PNAS. 99(8):5498-5502.

Prum, R. O. and Brush, A. H., 2002. "The evolutionary origin and diversification of feathers." Q Rev Biol. 77 (3), 261-295.

True, J. R. and Carroll, S. B., 2002. "Gene co-option in physiological and morphological evolution." Annu Rev Cell Dev Biol. 18, 53-80.

Thanks,

Psi

11:10 am  
Blogger Psiloiordinary said...

Ok so give us your definition of IC again please . . .

9:33 pm  
Anonymous Anonymous said...

What about this not being a mutation at all, but an inherent faculty that is only expressed in needed circumstances? A backup system?

Tennwriter

2:43 am  
Blogger Andrew Rowell said...

Psi,

I do not have access to a university library atm so a list of references to review articles is not very illuminating to me (or I suspect other readers of the blog) Can you summarize the relevant arguments of each of these papers or provide a link to a webplace where this has been done? That would be really helpful.

Many thanks!

10:36 am  
Blogger Psiloiordinary said...

OK I see.

. . .

Well why don't we cover off the IC issue first.

I think I can make my point with your previous definition and Lenski's findings which are all online and so easy for you to look at.

Will you give us your definition of IC again?

Hopefully we can make some progress then (don't you admire my optimism?)

Thanks,


Psi


BTW what happened to my replies to anonymous?

4:28 pm  
Blogger Andrew Rowell said...

Psi,

I didn't think your response to Anon was anything more than an insult really.

The last two posts have not been about IC at all.

I am happy to start another thread on IC but that is not what these last two threads were about at all.

9:00 am  
Blogger Psiloiordinary said...

OK I don't think I will bother at all then.

You won't engage and you just make accusations against my previous comments.

I don't know why you bother with comments at all.

Cheers,

Psi

5:37 pm  
Anonymous Cedric Katesby said...

OK I don't think I will bother at all then.
You won't engage and you just make accusations against my previous comments.
I don't know why you bother with comments at all.


Well said.
Andrew you have created an echo-chamber.
Just like all the other ID web-sites.

"I didn't think your response to Anon was anything more than an insult really."

Psiloiordinary is one of your most considerate posters.
You can't cut him a little slack?

Andrew, this is the...Internet.
People "insult" people all the time.

All you are doing is creating a "safe haven" for the wierdos.

Remember Steve, Sweden?
(Not exactly the sharpest pencil in the box.)
Or Dissenter?
"Anonymous"?
;(
Do you really want a web-site that promotes ID yet only attracts comments from intellectual train-wrecks like them?

It's true that I've made fun of them. It's true that I've delighted in exposing their ignorance. Yet I always gave them a chance. I always took their claims at face value and gave them plenty of room to spell out what they meant.
I was fair in the cut and thrust of debate.
Cruel? Maybe.
But fair.

If somebody wants to hang a sign around their neck saying "Hit me hard" then I will happily go off and find a cricket bat.

"Give the people what they want", that's my motto.

As I've said before, this is your site.
You get to run it how you like.
Yet if you just shut people like Psilo and myself down for "insulting" people, then you might as well not bother with the comments section at all.
All you will ever get are the "Steve,Sweden" types.
(Shrug)

8:05 am  
Anonymous Anonymous said...

Analysis not influenced by prior conditioning shows this:

(1) E. coli have been utilizing citrate in anaerobic conditions since Creation. This is nothing NEW. It was there all the time, just unseen. It has no relevance to origin of enzymes or catalytic pathways, let alone new organisms.

(2) Aerobic Citrate metabolism is thought to arise by co-option of a PRE-EXISITING transporter (tartrate transporter) which is DEGRADED to transport citrate as well. If anything, this is a LOSS OF INFORMATION.

(3) The elephant in the room is that E. coli remained E. coli after 31K+ generations. In otherwords, they don’t become anything else!

8:11 pm  
Anonymous Cedric Katesby said...

Analysis not influenced by prior conditioning...

Huh?
What analysis?

6:09 am  
Anonymous Cedric Katesby said...

Andrew,
This post is not directly relevent to the thread.
Feel free to delete.

Normally, I'd send this to you via e-mails but you don't have a contact address...so I'll contact you here.

Anyway...
There's an article on ID that has just come up.
It touches on a theme that you and I discussed before.
(Link)
After over twenty years, it's not going to suddenly get any better.

2:27 pm  
Blogger Psiloiordinary said...

I'm not going to comment on that comment because they just get deleted if they don't agree with the writer of this blog.

;-(

Psi

7:37 pm  
Blogger Andrew Rowell said...

Psi,

I don't agree with your last comment but I did not delete it...therefore your comment is not true.

9:47 pm  
Anonymous Anonymous said...

“I'm not going to comment ... because they just get deleted if ..don't agree with the writer”
Is it possible the you just cannot refute that the facts. What I’ve written is either true or false & shouldn’t be that hard to challenge on that merit or demerit. I’m not part of any editing but I can’t imagine anyone deleting rational arguments or statements of scientific fact. In my experience it’s abusive comments that get deleted (I’ve not seen any from yourself)

I make no secret of my stand on evolution: There’s plenty of evidence for micro, none for macro. Behe, Lenski’s & Ralph Seelke’s (spelling?) work show that macro probably does not & cannot happen. If someone shows me ONE instance of:

(1) Mutations producing codes where none previously existed

(2) Populations undergoing major transitions (not one form of E. coli to another form of E. coli)

I will accept that macro-evolution is possible. Number (2) should be possible to demonstrate in microbes as they have high mutation rates & short life cycles. The fact is we have never seen this & one has to question the warrant for believing it can happen. At least some proof of concept would go a long a way.

9:00 pm  
Anonymous decode said...

Psi,

...
The handle has one function and the bristles have another. To exchange one handle which has worn out with another - both of which have the same function is not evolution. Our cells wear out all the time and are replaced with others of exactly the same kind.

12:13 am  

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