Dr Tiffany Taylor, University of Reading
Listen Now Download as mp3 from the show Hacking biology - synthetic DNA and experimental evolution
Tiffany:: I'm an evolutionary biologist and I'm interested in experimental evolution. So, what that allows you to do is it allows you to – I'm using microorganisms or fast-replicating organisms that allow you to follow evolutionary processes happening in real-time.
Kat:: Because normally, when you think about evolution, you think about millions of years, population, stuff takes a long time. Give us an example of how many generations you can get through and what sort of timescale?
Tiffany:: Well, that’s the fantastic thing about bacteria is that they have a generation time approximately 20 minutes so you can get through vast amounts of generations very quickly and the population densities can reach huge scales in a very small space so you can keep large libraries of all sorts of mutants and you can grow them up. A great thing about it as well is that you can keep these mutants in suspended animation just by freezing them and then this allows you to compete evolved ancestral strains together and get those measures on like competition and fitness in different environments.
Kat:: Can't even imagine doing that with humans, so we dig up some Neanderthals and have a fight with them.
Tiffany:: Absolutely, yeah. So what you're doing is looking at survival of the fittest between like you say, fossils and highly evolved species and then letting them compete and fight, and seeing who wins.
Kat:: What are you particularly looking into?
Tiffany:: Well at the moment, I'm looking at the evolution of the novel genetic code. So what that means is that we’re getting a bacterial cell, we’re changing the code in some way and then seeing how the bacteria can evolve and adapt to this code over time.
Kat:: You're talking about changing the genetic code. Does this mean you're changing the DNA or something else?
Tiffany:: The way that the genetic code is read is in triplets. So, the genetic code is made up of different letters and each 3-letter codes code for different amino acid. So, for example, ATG is going to code for a specific amino acid. So if we change what that triplet code codes for, so it codes for a different amino acid, essentially, you're forcing the bacteria to read this genetic code differently.
Kat:: And so, you change it and then they have to figure out what on earth to do with it?
Tiffany:: Exactly. Then all we had to do is let them evolve over time just by transferring them to new environments and just then go back into the genome and have a look at what mutations have occurred to allow them to adapt to this new code.
Kat:: And you don’t really think of bacteria as being much under environmental pressure. What sort of different environmental pressures do you put them under?
Tiffany:: Well in the case of this one, the only real environmental pressure we’re putting them under is that we’re linking this trait to the production of a certain enzyme which is going to be vital for their survival in the environment because it’s going to have such a large fitness decrease associated with changing the code. You need to put a selective pressure which means it’s going to maintain this new code within the bacteria.
Kat:: But basically, if they can't evolve away of getting over this, they're going to die pretty fast.
Tiffany:: Exactly, yeah. Bacteria are very good at overcoming problems. I mean, they’ve been here for about 3 billion years, so I think that they probably will find a way and it is a bit of an interesting project that we really don’t know what we expect to see. But I would expect to see changes quite quickly and probably, quite inventive changes that we haven’t thought of before.
Kat:: And you're looking at bacteria, you're making them go through multiple generations, and mutating them. Are they ever going to change into anything other than bacteria because when you look at the billions of years of life on earth, we’ve seen species gradually evolve into different things? Are they going to change into something that’s not bacteria?
Tiffany:: It’s not possible in the timescales that we’re talking about. I mean, bacteria do replicate very quickly, but to see these sorts of changes in what we call the macro-evolutionary scale, to actually see them speciate, takes an incredibly long time and much longer than anyone’s career.
Kat:: Certainly longer than your post-doc!