Lenski's bacterial evolution genome evaluation

Lenski's experiment in bacterial evolution has been a PITA for anti-evolutionists ever since it began.

but now (in hte link above) it has been frther analysed using tools that did not exist when it wa started - whole genome analysis.

The team behind the latest work took advantage of the fact that the experiment has involved taking snapshots of the bacteria every few thousand generations, simply by siphoning a few off and sticking them in the freezer. These bacteria can be used to figure out what the status of the genomes were at a given generation, or even grown again, to see whether the same evolutionary history can take place.

In the new paper, the authors sequence the genomes of 29 different clones of bacteria, obtained from various points in the culture's history. One distinct genetic lineage appeared in the culture a bit before 10,000 generations but had apparently died off before 20,000 generations, never to be seen again (the authors called this UC, for "unsuccessful clade"). Three large groups of related strains still persist in the cultures, but only one of them has citrate-eating bacteria, which evolved sometime around 31,000 generations in.

that's the background - but the most intersting bit is this:

The genomes also let the researchers figure out exactly how citrate eating evolved. The E. coli used in the experiment actually have a gene that brings citrate inside the cell, but it's normally shut down when oxygen is present. In the first citrate eaters, a bad duplication of this gene made an extra copy, but put it under the control of regulatory DNA for a neighboring gene. This worked, in that the new control sequence expressed the gene even when oxygen was around, but it didn't work well. The resulting bacteria only had a one percent advantage in reproductive success relative to their peers.

One of the main "questions" anti-evolutionists have had is "how does evolution work - what is the mechanism??" - I think this answers that pretty well.

Hooray for science.

Great find OP this is really cool. And opens the door for many other advancements. While this is just bacteria, I would imagine the same principals could be applied to other organisms. It should also lead to faster and cheaper genetic modification studies and experiments.

One of the problems for people that don't accept these things are definitely a lack of understanding molecular biology, and grasping the influence of time.

It is an excellent experiment, but unfortunately still not enough to convince opponents, because it only deals with things they can't see, ie. bacteria.

Originally posted by watchitburn
Hooray for science.

Great find OP this is really cool. And opens the door for many other advancements. While this is just bacteria, I would imagine the same principals could be applied to other organisms. It should also lead to faster and cheaper genetic modification studies and experiments.

Oh it's nothing new. This mechanism (gene duplication and subsequent mutation) is very well known. The vast majority of our genes are the result of this exact thing. Moreover, at least in eukaryotes, protein-coding genes also evolve in "modules". Like in the amino acid sequence, there are specific domains and then intervals that don't do much. These domains have gotten suffled around massively. As to this study, I think the novelty was that they observed gene duplication and subsequent gain of function happening in "real time".

reply to post by rhinoceros


Thanks, I did not know that.

But I would think being able to observe the changes in real time, seeing what exactly led to what and how the changes initiated will be very helpful for future studies.

I done that many times in lab, sometimes because of screw ups.. for example. if you grow the bacteria in really really low level of penicillin, that damages them but doe snot kill, they will eventually learned to resist and grow in a low level penicillin without a problem, and you can do this for generations and bring them to a decent level of penicillin resistance. But, if you take away the antibiotic infused medium, and grow them on plane nutrient agar, they will slowly lose their resistance over time(over generations).

But guys... this won;t be enough, that's why the Anti people divided evolution into different types of evolution, so they can say this is micro-evolution and still discredit evolution.

A smart person will not differentiate evolution. These are a small picture of the grand evolution.

The genomes also let the researchers figure out exactly how citrate eating evolved. The E. coli used in the experiment actually have a gene that brings citrate inside the cell, but it's normally shut down when oxygen is present. In the first citrate eaters, a bad duplication of this gene made an extra copy, but put it under the control of regulatory DNA for a neighboring gene. This worked, in that the new control sequence expressed the gene even when oxygen was around, but it didn't work well. The resulting bacteria only had a one percent advantage in reproductive success relative to their peers.

You do realize that this is the result of a knockout mutations breaking the regulation of the already present citrate transport mechanisms, allowing citrate to be transported under both oxic and anaerobic conditions.

In simpler language.

E.coli already had all the equipment needed to eat citrate. All it needed was to be able to get the citrate into the cell under oxic conditions. A bunch of mutations broke the regulatory mechanisms allowing it to happen in this environment.

This is the result of loss of function, no new functions emerged.

Sorry to rain on your parade folks.

Bacterial resistance is much more interesting than the old random mutation and natural selection thing. There's many more amazing things happening than what is shown in the citrate example, which is a good example of what random mutation can do..
Absoluteism is the enemy of scientific discovery.

Here's a clue. Small but not stupid.
Descent with modification, random, gradual? Well, not quite.