Nick Lane

It doesn't quite have a meaning.

So this is the kind of dynamic of bacterial evolution, is they retain small genomes with access to large pangenomes, and they're forever borrowing, matching, and so on.

And they effectively remain competitive by keeping their own genome pretty small.

And then eukaryotes kind of threw all of that out and got larger genomes.

And then the question is, well, if you try and do that with a large genome, a eukaryotic-sized genome, and then you go on picking up little bits of DNA from the environment, the chances of you replacing the right gene gets lower.

Right.

So it just becomes less and less efficient the bigger your genome is.

So by the time you get to eukaryotes, they have a large genome.

Why do they have a large genome?

I would say it's because you acquire this endosymbiont and they become the mitochondria.

Now you have a lot more energy available.

There's all kinds of reasons why eukaryotes will tolerate a larger genome.

But the bottom line is you've got the energy to do something with it, which bacteria never really had.

And so now lateral gene transfer is just not good enough to maintain this larger genome.

You're going to have to do something more systematic.

So you pull on an entire genome.

You line everything up.

You cross over between them.

Now it's systematic.

It's reciprocal.