[Q] But the work on conjugation, was to clarify both prophage and its location, but...
It was reciprocal, meaning that the two worked together. In fact, we set off to try
to understand prophage, but very quickly, it enabled us to study the exact mechanism
of genetic recombination, of conjugation and of recombination.
[Q] And can you tell us about the principle of the experiments you did
at the time, about uninterrupted conjugation?
Yes, so that was... What we noticed was that...
let me see how all that came about...
[Q] I know that William Hayes had found strains, it was quite important, wasn't it?
Yes, there were strains... In the Colon Bacillus system, there were males and females,
there were donors and receivers. The majority were low frequency donors,
meaning that there were recombination with ratios of 10-6,
but there were particular donor strains that had been isolated, on the one side,
by what was his name? The Italian who worked on... Cavalli Sforza and on the other side
by Hayes, who injected markers at much higher frequencies.
So we tried to analyse it and Elie had the idea of separating the happy couples
during conjugation by placing them in a waring blender.
By marking proteins with S35 or nucleic acid with phosphor, they tried to see
what did and what didn't go in the phage particle.
And they showed that it was the nucleic acid
that went in and that the protein came out. So, we tried to do that with conjugation,
and we noticed that... let me see, how did this come about?
[Q] From an outside perspective, I imagine that
you saw that specific markers were going in at different times.
Yes, that's right. The aim was to separate them to see when the chromosome went in.
We would mark it either with sulphur or with phosphor, and the idea was that
conjugation should occur. And at some point, the male chromosome is going to end up in the female.
And when we had done that, and we had separated them at different times,
as it happens we separated some at 10 minutes and others at 30 minutes,
and the results were different. And we noticed that if we separated them
in a abrupt manner at different times, we would see that the chromosome went in
through one end. It was the so-called spaghetti experiment which infuriated Wollman.
[Q] The chromosome being a long spaghetti that enters the bacterium... And afterwards,
you found that depending on the bacterial strains, the same yet slightly shifted order could be found.
That's right. It has a name. A permutation. To permutate, yes.
In other words, the only way of explaining it, is to put it all in a circle
that would be open at different ends, the opening being the front and the back.
[Q] Which at the time was revolutionary, wasn't it? Yes, the circle was revolutionary. The idea...
I remember the first time I told Elie that the chromosome was circular, he was beside himself.
I don't know why but he was furious. Then he accepted it.
The idea of a circle wasn't obvious. It was already clear for the phage.
We knew that phage chromosomes were circles.
But, it was quite a nice explanation,
a circle that you open at different points and that goes in, it wasn't bad.
It held out.