Well, welcome, everybody, for the third session

of this meeting on synthetic biology. So I'm the chairperson of the third session. Actually, I know very few people here, because I, myself, I'm neither a mathematician nor a biologist in the strict sense. Actually, I am an evolutionary biologist. And it's actually a great pleasure

to hear that evolution pops up in some of the discussions before. So I'll use the few minutes that I can use as the chairperson of this session to try to explain to you why synthetic biology could be interesting also for people in my background,

and it's ecology and evolutionary biology. Oh, sorry, is that better? OK, so I'm going to try to explain how why synthetic biology can be interesting also for people in my area of evolutionary biologists. So we're now here on a meeting on synthetic biology.

So most people think of it in terms of Frankensteinian science. So actually, one of them, this is an image of a salamander larvae, which they gave another eye. So it's not evolutionary, but it's synthetic.

They've implanted another eye. And these salamanders can actually do very well with it. The other thing is it's real, but it's not science. It's art. It's an artist from Australia who has implanted an ear in his arm, and he wants actually to put a microphone in it to do some art and things. So for most people, when you talk about synthetic biology,

that's what they tend to think about, scientists, mad scientists interfering with things that they shouldn't interfere with. But anyway, I think that the whole aim of this meeting is to show that it's a respectable science

and that we can actually use it for many ways. Of course, we have had already an engineering point of view where we can actually use all sorts of insights to design, modify natural systems in order to do things that we want them to do. I want to stress here that we actually also can use,

we could use synthetic biology to gain insights in how things are. So I'm an evolutionary biologist, and much of my day-to-day work is to deal with mathematical models that try to predict the outcome of evolution. And it turns out that most of this, much of this

rests on hypothesis that we make about trade-offs between trades that individuals have. And all these examples actually date from the 60s of the previous century, where people were asking themselves what makes that some organisms are generalists

that live in the whole environment, whereas other organisms are specialists. They specialize on special types of environments. And it turns out that the end result depends on basically what is possible for the organism. If you can have a, now I have to try to find a pointer.

So you can have two types of environments, and you can measure the fitness, the degree of adaptedness to these different types of environments. And you can sort of make a line where all the maximum fitnesses

that the individual is able to attain. So it can choose a point somewhere on this line, and it's this trade-off shape that determines what basically is possible for this organism. Well, it turns out that the end result, evolutionary end result, depends very much on the shape of this line. So here in this case, you can have a shape which is concave,

but you can also have a shape which is more convex. And it turns out that the end result, the evolutionary end result, is here sort of represented by the blue dots, is a generalist population. If this trade-off shape is convex, whereas you get two specializing populations

if the trade-off shape is concave. So this gives us an insight, after this, the evolutionary biologist, this gives us an insight to what might be the conditions that favor specialization of organisms. But now you want to test this kind of prediction. And then you're going into the field, my colleagues go into the field,

and they say, well, let's go and try to see what is the shape of this trade-off function. Well, if you do this, this is typically what you get. Either you have one single population and you get sort of a cloud around a single population of journalists, but it's very difficult to gain insight in what precisely determines the shape. Is this indicative of a convex shape or a concave?

And similarly for the concave, in this case you have two distinct populations, and we have actually very little information about what might be the trade-off shape in between.

Now, people have already started doing things like genetic engineering to gain insights in this kind of question. And you can take a bacterium and you can tinker with its basic physiology. I don't know the precise details, but it means that if you interfere with the production of the expression of different genes,

you can switch on different types of responses in a bacterium. I think this is E. coli. And by interfering with this, you can actually sort of make the organism. You can create many different strains where the expression levels of these genes are modified.

And you can quite neatly trace out the shape of these trade-off functions. So I think synthetic biology could be used to get this even a step further and to make us address questions like evolutionary biology, what is actually possible?

So this is one of the questions I think that we should add to this list that Victor already wrote on the blackboard earlier on. And then if we know what is possible, we also have to work out why it isn't there already. And I think this is also a question that arose more or less during the discussion earlier today.

So I think this is a very short outline of why synthetic biology could be of interest for people in my area, evolutionary biology. But it really means that we should address questions like dealing with evolution. So my session, during this session, actually also because of the chairperson of tomorrow

couldn't come so I'll be chairing the next morning as well. My session of these two sessions continue on the theme of what you can do if you change the genetic code. And there is actually in evolutionary biology there's a related question that pops up all over the place

and that's actually why actually do organisms use a common code? This is, if you think about it, it's not obvious at all. Of course, we have seen the dogma, the famous dogma already a couple of times today, which says, well, you have DNA and then everything follows from this.

But actually lots and lots of research nowadays shows that this dogma is not so infallible as it has seemed, as of course we know about reverse transcriptase for a long time. But nowadays lots of genetic information is actually not coded in DNA but in epigenes that are modifications, short-term modifications of DNA.

And these have a much more fluid way of encoding information. And so it really means that genes are not so universal as is often thought. I stumbled on a question like this already a long time ago when we were doing a model

on the evolution of information use in a population. And it turns out that you have a system will evolve to use a single way of encoding information only if the members of this population are not too much in conflict. If the members of this population are in conflict,

that's what you have, is that the whole thing becomes unstable and you get cyclic evolution or chaotic evolution where you have different types of encoding get evolved. And in human populations you can already see this, here we are all very nice people so we don't have much conflict here

so we can manage all by speaking English. But if you go to the market or some other economically important area you will discover that people tend to speak in codes where they try to convey some of the information to try to address, send information only to particular people and not allow everybody to hear. So in this case common code will not evolve.

And actually there's some examples in biology where the common code is actually aborted, for instance where populations interact with parasites and viruses and things. So and then you can actually arrive at the situation where the whole information use breaks down.

So and there's the second case over here. So we were discussing standards earlier on. Actually I think there should be also a reason, we should also be aware that there's an advantage of having a standard but it's also, it can also be an inconvenience. But you always have to worry about where you are and you always have to worry about the costs

and benefits of standardizing and efficient communication. Okay so that was actually what I had to say today.

So I'll now leave the floor to Florif Rom's work and we're going to talk about semi-synthetic organisms, if I'm correct.