I think of myself as a bird man or a fruit fly man, I don't know anything about bacteria, I never did a course in... in bacteriology or microbiology in my life. But it so happened that, almost 10 years ago now, my wife was working in a lab next door to a group of people who were working on antibiotic resistance in bacteria. And they, I think, initially thought it was a problem in protein chemistry, what is it that was changed about the enzymes that made them resistant to penicillin? But they increasingly, I think, realised that they were working on a problem which had to do with evolution, and very rapid evolution. And Sheila suggested to them that they might actually not be wasting their time if they came to talk to me about it. And it was great for me, because for the last five years I spent most of my practical working time actually thinking about just this problem. And, you know, I get my first hands on the data and I'm able to think about it. And it is actually... rather, it's almost eerie, actually, the way that penicillin resistance has spread round the world in bacteria, in 50 years, since the first serious clinical use of penicillin. And now that we can actually sequence genes, and, sort of, trace them, we can actually give a history of it in some cases. Bacteriologists have the nice habit, when there's an epidemic of something, they isolate the bacteria and they put some of them in the deep freeze, so that it's as if all your fossils are in the freezer and when you want to know what their genes are you just pull them out and sequence them. It'd be lovely if you could do it with dinosaurs, but you can't. But here we've got an evolution... a bit of evolutionary history where we can actually go to the freezer and take out the ancestors and have a look. And in streptococcus, which was the first bacteria which they really worked on, it's actually a very sad story, that the first genes, the first bacteria resistant to penicillin, were found in New Guinea and in the northern part of Australia, but particularly New Guinea, in the years immediately after the war. And what happened was that foreign troops, both Australian troops and Japanese troops had been in New Zealand... in New Guinea and had infected the natives with respiratory diseases caused by streptococcus, to which they were totally unresistant and were really suffering seriously from respiratory diseases. And it's almost fair to say that New Guinea was sprayed with penicillin... I mean, it was used in a sort of mass, uncritical way. And it, in the short run, was effective - it did indeed cure the diseases, which is good. But the first resistant streptococci emerged during that period. And they did so in an interesting way. They did it by sex, and we can do that by sequencing the genes and looking at the genes responsible. And it turns out that the so-called Penicillin Binding Protein Gene, which is the main one that changed, has received a great insert from somewhere, by which I mean, most of the gene in the resistant and the sensitives are identical, but a piece of some hundreds of nucleotides in the middle of the resistant strains is quite different from the sensitive ones. And you can say, that bit's come from somewhere. In streptococcus, we still don't know where it came from. Though, in the second bug we looked at, which is neisseria, which is a cause of meningitis and gonorrhoea, we do know where the gene came from and we know where the insert came from - it's exactly the same story, a piece has come in, and we can identify the source.

[Q] From a different kind of bacteria?

From a different kind of bacteria. In the neisseria case, it came from perfectly harmless relatives of neisseria, they're also neisseria but they're not causing meningitis or gonorrhoea or anything like that. And I wouldn't be a bit surprised if two or three of us in the room right now had it in our throats. They're quite harmless commensals. And they just happened, by chance, to be resistant to penicillin.