50,000 generations of bacteria prove that evolution never stops

In a remarkable experiment that's been going on for nearly a quarter century, biologists have shown that lab-grown bacteria — even in a stable, unchanging world — will continue to evolve in a way that makes it increasingly good at reproducing


Back in 1988, evolutionary biologist Richard Lenski took some E. coli bacteria and put them in a dozen glass flasks. These 12 populations of bacteria have been there ever since, eating and dividing in isolation — over and over and over again. Now, some 25 years and 50,000 generations later, the strain has demonstrated some very noticeable changes.

What he and his colleagues at Michigan State University in East Lansing discovered was that, even in the static, boring lab flask, the bacteria never stopped evolving.

On it's own this may not sound surprising. Evolutionary theory would suggest that, even in the absence of any kind of selectional pressures, genes will slowly drift and degrade over time; there's very little to reinforce the integrity of genetic traits outside of basic biological functions, like replication.

But computer models have shown that animals can still experience significant evolutionary changes over time, even in the absence of selectional pressures. Traits like evolvability, or evolutionary potential.

Read more at i09


The researchers had originally thought the bacteria would reach a limit where it couldn’t improve any further it was thought that would happen around the 10,000 generation. But now they are at the 50,000 generation and it just keeps on evolving. In fact it is doing it faster now and that should continue.

On left is a petri dish with equal numbers of colonies of two different bacteria. But over time, after competition and evolution, the lighter ones (at right) have taken the lead.

The researchers observed that the mathematical pattern matched a power law; the bacteria will continue to improve for as long as the laws of physics will allow, but at an increasingly diminished pace

reply to post by Grimpachi


Wow. But I really doubt there's any such thing as a stable unchanging environment. What about gamma rays or subtle shifts in the magnetosphere? Just for starters.

EXCELLENT find. Bravo. Thank you. You get every flag and star I'm allowed to give you.

This is fascinating. It reminds me of a post on here a while back about a mosquito species that evolved to live in subway tunnels in the UK. I wonder how much those bacteria can change before they are considered a different species?

reply to post by Grimpachi


And speaking of selective pressures. Do you think it's possible (maybe likely) that humans are evolving to be more stupid? Given the state of the world and mankind's role in creating crises, as wellas the fact that stress kills both the libido and physical body, it makes a lot of sense to select for stupidity and the attendant oblivion. ...Dontcha think?

reply to post by soficrow


It is possible but I think it is more likely to vary from region to region. I don’t think our species as a whole is evolving to be dumber but I do see social stresses on the US having an effect that may not be true for people in places like South America. The earth is a big place and there are just too many variables to generalize like that IMO.

reply to post by Grimpachi


Okay. Maybe we could consider unseen selective pressures acting on the isolated e.coli in their little flasks. Seriously. I do think there's a lot going on environmentally besides what we've learned to measure. But we can stick with the measurable stuff.

reply to post by Grimpachi


Indeed... you have to be quite ingnorant to
think anything else!

Thanks for posting this.

I have a big soft spot in my heart for Richard Lenski after his part in the Lenski Affair, which humiliated Andy Schlafly, the idiot behind Conservapedia.

reply to post by AngryCymraeg


Awesome I hadn’t heard of that before. I think I am a fan now myself. Thanks for posting it.

Space Experiment
You oughta see what happens to them little boogers in space.

I couldn't readily find the article I was looking for. That one had them directly exposed ... and they thrived ... even becoming deadlier.

Another good one, Grimpachi!!

Grimpachi
reply to post by AngryCymraeg

 

Awesome I hadn’t heard of that before. I think I am a fan now myself. Thanks for posting it.

No problem. The whole thing was immensely amusing.

AngryCymraeg
I have a big soft spot in my heart for Richard Lenski after his part in the Lenski Affair, which humiliated Andy Schlafly, the idiot behind Conservapedia.

That was classic! Thanks for the link.

I like kicking the proverbial sand on scientists at the metaphoric beach, but it's just for fun. Most of these guys are truly brilliant and if they got serious they could virtually melt you with their intellect. I have learned (being the big dummy that I am) that there's a line you can come up to, but you better not cross it. Up to that line though, it's a hoot.

so what did they change/evolve into?

are they still not bacterium?

Grimpachi

In a remarkable experiment that's been going on for nearly a quarter century, biologists have shown that lab-grown bacteria — even in a stable, unchanging world — will continue to evolve in a way that makes it increasingly good at reproducing


Back in 1988, evolutionary biologist Richard Lenski took some E. coli bacteria and put them in a dozen glass flasks. These 12 populations of bacteria have been there ever since, eating and dividing in isolation — over and over and over again. Now, some 25 years and 50,000 generations later, the strain has demonstrated some very noticeable changes.

What he and his colleagues at Michigan State University in East Lansing discovered was that, even in the static, boring lab flask, the bacteria never stopped evolving.

On it's own this may not sound surprising. Evolutionary theory would suggest that, even in the absence of any kind of selectional pressures, genes will slowly drift and degrade over time; there's very little to reinforce the integrity of genetic traits outside of basic biological functions, like replication.

But computer models have shown that animals can still experience significant evolutionary changes over time, even in the absence of selectional pressures. Traits like evolvability, or evolutionary potential.

Read more at i09


The researchers had originally thought the bacteria would reach a limit where it couldn’t improve any further it was thought that would happen around the 10,000 generation. But now they are at the 50,000 generation and it just keeps on evolving. In fact it is doing it faster now and that should continue.

On left is a petri dish with equal numbers of colonies of two different bacteria. But over time, after competition and evolution, the lighter ones (at right) have taken the lead.

The researchers observed that the mathematical pattern matched a power law; the bacteria will continue to improve for as long as the laws of physics will allow, but at an increasingly diminished pace

Isn't this a bit a stretch to say that the E. coli bacteria were evolving while in reality were "good at reproducing"?

Furthermore, how is this evolution if the bacteria are still confined in the same structure as they were albeit a lot faster in "reproducing" new generations of bacteria?

As noted:

the bacteria will continue to improve for as long as the laws of physics will allow, but at an increasingly diminished pace

So at a diminishing pace, I wouldn't be surprised that eventually they will suffer the fate of those that preceded them.


No longer able to "reproduce".

Hence - no evolution.

reply to post by edmc^2


Sorry but I do not care to turn this thread into yet another class on what evolution is.

Furthermore the deminishedpace they are referring to is talking about the time between generations. It has been speeding up. The opposite of slowing down.

Grimpachi
reply to post by edmc^2

 

Sorry but I do not care to turn this thread into yet another class on what evolution is.

Furthermore the deminishedpace they are referring to is talking about the time between generations. It has been speeding up. The opposite of slowing down.

No need to. As an avid reader of TalkOrigins I'm well aware of what is evolution is about. But reason why I'm questioning this study is for the simple fact that "changes in the frequency of alleles within a gene pool from one generation to the next" is not evident but assumed.

As mentioned "Lenski's team believes that similar patterns would likely apply."

Furthermore, the E. coli bacterium remain the same after 50,000 generations.

reply to post by edmc^2

So at a diminishing pace, I wouldn't be surprised that eventually they will suffer the fate of those that preceded them. No longer able to "reproduce". Hence - no evolution.

Funny.

"hence - No evolution", even funnier.

What that quote from the articles says is that in a lab setting, test tube or petri dish, as the bacteria grow and grow, the competition for space and food will increase, due to that they will come to a almost complete stop in growth. If the area is bigger they will grow until they occupy and used up all the resources.

We use this what we call a McFarland standard to estimate the turbidity of overnight culture to see if they reached their maximum growth, usually 10^9 to 10^11.

reply to post by edmc^2

Furthermore, the E. coli bacterium remain the same after 50,000 generations

I don’t know what you think the definition of same is but you are wrong. It did not remain the same.

Now, some 25 years and 50,000 generations later, the strain has demonstrated some very noticeable changes.

it got faster and faster at reproducing. And remarkably, the bacteria showed very little signs of slowing down.

Grimpachi
reply to post by edmc^2

 

Furthermore, the E. coli bacterium remain the same after 50,000 generations

I don’t know what you think the definition of same is but you are wrong. It did not remain the same.

Now, some 25 years and 50,000 generations later, the strain has demonstrated some very noticeable changes.

it got faster and faster at reproducing. And remarkably, the bacteria showed very little signs of slowing down.

Aren't we splitting hairs here? The same is the same. Meaning, to be very specific - a bacterium.

As for the changes that you're alluding to - again the change is NOT in the "alleles (genes)" but in their ability to reproduce.

To quote:

it got faster and faster at reproducing

Why is that?

For obvious reasons - competition or to be exact lack of competition.

As mentioned:

But over time, after competition ..., the lighter ones (at right) have taken the lead. Image...

Note - "...and evolution," according to whom?

Surely not based on facts but on "belief" - assumption.

luciddream
reply to post by edmc^2

 

So at a diminishing pace, I wouldn't be surprised that eventually they will suffer the fate of those that preceded them. No longer able to "reproduce". Hence - no evolution.

Funny.

"hence - No evolution", even funnier.

What that quote from the articles says is that in a lab setting, test tube or petri dish, as the bacteria grow and grow, the competition for space and food will increase, due to that they will come to a almost complete stop in growth. If the area is bigger they will grow until they occupy and used up all the resources.

We use this what we call a McFarland standard to estimate the turbidity of overnight culture to see if they reached their maximum growth, usually 10^9 to 10^11.

So competition is evolution?