Nick Lane

Eukaryotes have that, and it's kind of an interesting question.

Why would you have such a big, unwieldy genome?

It takes longer to copy and bacteria are really streamlined.

They get rid of genes they don't need, and then they can grow faster.

But now the conditions change.

Now you need this gene.

So what do you do?

You pick it up.

You just pick up random genes and hope for the best.

Pick up the right one and off you go again.

So bacterial genome sizes are small.

They've got what you'd say is a small genome, but then a large pan genome, which is kind of all of the genes they have access to.

So an E. coli cell might have 3,000 or 4,000 genes in a single cell, but access to 30,000 or 40,000 genes.

Why doesn't everybody just converge to this streamlined thing that is needed for the current- I mean, I think what keeps the metagenome around is the fact that different strains of E. coli, whatever bacteria they may be, are living in different environments.

So you could have a commensal bacteria living in your gut.

You could have bacteria's E. coli living on your skin, very different environment.

You can then have non-commensal pathogenic E. coli, which are behaving differently.

Again, they can differ in 50% of their genome.

So you've got all of these things going on side by side, and they can all borrow genes from each other.

And this is basically within the same species, whatever species exactly means with bacteria.