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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.
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.
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.
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.