9UNP0212SD_James Crow_Millard Susman_WordPress

- Welcome, everybody, to Wednesday Nite at the Lab. I'm Tom Zinnen. I work here at the University of Wisconsin-Madison Biotechnology Center. I also work for UW-Extension Cooperative Extension. On behalf of the Wisconsin Alumni Association and the Biotech Center, welcome to Wednesday Nite at the Lab. We do this every Wednesday night, 50 times a year. Tonight, it's an especially great pleasure to be able to introduce our two speakers on a rather auspicious occasion. This week is the 50th anniversary of the awarding of the Nobel Prize in Physiology or Medicine to Professor Joshua Lederberg, who at the age of 33, won the award back in 1958. As Professor Susman said, for the discovery of sex in bacteria. 

And if you put the pause in there for just right, it's actually funny, except for the people from Minnesota. 

(light laughter)

 Professor Millard Susman is one of our speakers tonight. Professor James Crow is the other. They're two of the most illustrious professors we have. They're also two of the finest storytellers. That's why it was so splendid for me when they both agreed to give the talk tonight on Joshua Lederberg's life, his research here, his research beyond UW-Madison, and impacts of the discoveries he made that still reverberate through microbial genetics today. So I believe you're going to go first. Please join me in welcoming Professor Millard Susman to Wednesday Nite at the Lab. 
(applause)

- Well, it's a pleasure to see all of you, and have you all join in the celebration of this remarkable achievement of the University of Wisconsin faculty member, a colleague of Jim's, and almost one of mine, Joshua Lederberg. I came here a little bit after Joshua Lederberg left the University of Wisconsin. And I inherited his lab. So I had pieces of equipment. I had pieces of furniture that had little labels on them that said Joshua Lederberg. And he was such a holy figure by the time I came and joined the faculty here, that I hesitated to sit in any chairs or touch any equipment. It took me a while before I managed to begin to feel comfortable in the Lederberg laboratory. I'd like to give you a sort of lightning tour through Josh's life. And then, Professor Crow is going to tell you a little bit, give you a little bit more intimate picture of Joshua Lederberg. 

And then I'll come back and try to teach some science at the end of this session. So, let's begin. Joshua Lederberg, that's his picture showing him here in a laboratory at the University of Wisconsin. He was born in May, 1925, and died just earlier this year. This is his mom and dad. They moved to the United States of America from Israel in 1924. And a year later, Josh was born. His father was a Rabbi, and hoped that Joshua would become one. But Joshua had other ideas. And by the age of five or six, he said he knew he wanted to be a scientist. 

And by the age of 10 or 11, he was reading biochemistry texts. He was rather an extraordinary child. Here he is with his mother. And here's where he went to high school. That's Stuyvestant High School in New York, which is a science high school, and proud of many distinguished alumni, but surely none more distinguished than Joshua Lederberg. He then went to Columbia University. He worked with a famous bacteriologist named Francis Ryan. I'll show you a picture of him in a minute. After doing research with Francis Ryan and learning how to work with microorganisms, he went to medical school at Columbia University, but got interested in doing research. He went to work at Edward Tatum's lab at Yale, where he did the research that demonstrated that bacteria, two E. 

coli bacteria, the kind of bacteria that you read about in headlines. And these were bacteria that lived in the normal human intestine, that these bacteria could cooperate to produce offspring that had genetic attributes of both parents, when you mix these together. That's what we call a genetic recombination or sex in bacteria. So from a geneticist's point of view, the ability of two parents to produce offspring that have characteristics of both parents is sex. And I can't make it any more exciting than that. 

(laughter)

 This is a picture of Francis Ryan, who was Joshua's undergraduate research advisor. He started to try to work on doing a kind of experiment that I'll talk about later, called transformation, where you transfer genetic traits from one strain to another, just by extracting DNA from the donor strain, and applying it to the recipient strain. And he was trying to do that with a fungus, Neurospora. He failed to do it. 

And Ryan suggested that he might like to go and work in the lab of this man, Edward Tatum, where he could try it with bacteria, with E. coli. And when he went to Tatum's lab, he demonstrated the existence of sex in bacteria. That led to the Nobel Prize. So this was work that he did before he got a PhD degree. He was an unofficial graduate student in Tatum's lab. And he did an experiment that ultimately got him to Stockholm. In 1947, after receiving a PhD from Yale, the story is that he was going to go back to medical school. He completed these nice experiments on demonstrating sex in bacteria with Tatum, decided he was going to go back to medical school. Tatum said, you know, what you've done is good enough work to win your PhD. 

If we could get you retroactively registered as a graduate student at Yale, and we could convince the faculty that you've done reasonably scholarly work, we might be able to get you a degree. Then you could get a job that's better than being a doctor. And they did that. They got him permission to register retroactively as a graduate student at Yale. He got his degree on the basis of two year's work done as a visitor in Tatum's lab. And he got a job at the University of Wisconsin. So, thanks to Tatum having talked him out of getting an MD degree, Joshua ended up here. This is a picture of one of his first graduate students, Norton Zinder. In fact, I think he was perhaps his first graduate student. And Norton Zinder, working with the bacterium Salmonella, discovered that sometimes it's possible to transfer genes from one bacterium to another by growing viruses on the first bacterium, and then using the viruses that are produced by that bacterium to infect the second strain of bacteria. 

That's a process, transfer of genes by virus, that's called transduction. And Norton Zinder, who became a professor at Rockefeller University was the graduate student who made that discovery in Joshua's lab. This is one of the major discoveries of bacterial genetics and was one of many earth moving discoveries that were made in the Lederberg lab. When Lederberg came to the lab, he had, this was not a second or third or fourth wife, this was a new wife in the sense that they had just recently been married. And his new wife, Esther, came and enrolled as a graduate student in the department, not under Josh, since she was married to Josh, but under RA Brink, who was a professor in the department. But she worked in Josh's lab. She did some very important research that again, I'll talk about later, that has to do with the mechanisms of evolution in bacteria. The work that Josh did at the University of Wisconsin was enough to earn him the Nobel Prize in 1958. He was 33 years old at the time. And these are the three scientists who won the Nobel Prize that year, George Beadle, Edward Tatum and Josh Lederberg. 

I was a graduate student at Cal Tech. George Beadle was the chair of our department at the time. So, needless to say, we were thrilled to have the chair of our department win the Nobel Prize. Beadle and Tatum had more or less opened the whole field of biochemical genetics, it was called, through collaborative work that they did. And we consider that Tatum was a legitimate winner of the Nobel Prize, but we were kind of jealous of Lederberg having won the prize, because after all, we wanted to get as much credit for our local guys as we could. So my major professor sent telegrams to Beadle telling him to kind of show Lederberg off to the side. He had a big "Lederberg Go Home" banner produced and sent to Beadle. But Lederberg, you'll see, got half of the prize. And Beadle and Tatum had to share the other half of the prize. So in the eyes of the Nobel committee, Lederberg was the big winner. 

In the year 1958, the year that he won the Nobel Prize, Josh decided to take a job at Stanford, to leave the University of Wisconsin and go to Stanford. But by the time he went to Stanford, he had really done most of the work that he's famous for today. It was all done here. There's a building across the Henry Mall, which now says, I forget what it says, I think it says Life Sciences Communication. It used to say Genetics. Before that, it used to say Agronomy. Anyway, the building in which Josh did most of his work is the building directly across the Mall in the middle of those buildings, what is now Life Sciences Communications. The old, old, Genetics building. And then Josh went to Stanford. He came back here in 1967 to receive an honorary degree from the University of Wisconsin. 

And on that occasion, he gave his Nobel medal to the University of Wisconsin. This is Josh. That's the medal. This is Jim Crow, whom you're about to hear speak. That's Fred Harvey Harrington, who was the president of the University of Wisconsin at the time. And that's the Nobel medal that Josh gave us. I probably shouldn't tell you this, but we've misplaced it. We don't know exactly where it is. Presumably, it still belongs to the university and is in safekeeping somewhere, sort of like Vice-President Cheney. 

(laughter)

 Now, while he was here, before he left he organized the Department of Medical Genetics, which became an important department at the university. One of the first things he did as a new faculty member here was to meet Jim Crow at a meeting and talked the faculty into recruiting Jim to the University of Wisconsin, which next to recruiting Josh Lederberg, may be even more important than recruiting Josh Lederberg, has been a blessing to all of us in the department and in Madison. Josh served as chair of the Department of Medical Genetics for two years and then left for California. And then in 1970, he moved from California to Rockefeller University as president, and held that position for 20 years. In addition to being a microbiologist, and extraordinary geneticist, he was interested in all kinds of other scientific issues. One of the scientific issues he was interested in was the possibility of life on other planets, or life elsewhere in the universe. He was one of the first people to suggest that in exploring space, in sending rockets to the moon, or sending exploring tractors to Mars, we ought to be careful that we sterilize all of these things so that we don't contaminate foreign objects, foreign bodies in space with Earth organisms. And he also was concerned about bringing things from space back onto Earth. So he made a big issue, and he was the first to do so, being sure that there were strict policies of quarantine on both outgoing and incoming space objects. He coined the word exobiology, which was pretty popular for a while. 

It's now become astrobiology. He helped design equipment for doing chemical analysis of soils on other planets. And he was one of the people who invented a new approach, a new computerized approach to analyzing information acquired using a mass spectrometer, to see what kinds of organic molecules were present in the soils of various planets, moons, and so forth, to see if there was any evidence that there were living things on those planets. So they could take remote data from these devices, mass spectrometers, to try to find evidence of chemicals of life on other planets in our solar system. He was very much interested in public policy on various issues. One of them, biological warfare. He was one of the first to call to the attention of the federal government the possibility of biological warfare was a serious issue that had to be considered by government. He became an advisor to the government, participated on a lot of government panels on the subject, helped with negotiations with other countries. And he played a very important role in public education. And for a number of years, he wrote a column, five years, he wrote a column called "Science and Man," in the "Washington Post," which was intended to inform the public on a wide variety of scientific issues. 

So he, for a good many years of his life, devoted a tremendous amount of his energy to teaching science to the public. I don't know when my next picture is going to come up. This is a huge picture. But I just wanted to show you what Josh looked like over the years, then I'll sit down and let Jim talk for a while. Well, when this next picture comes up, it's a picture of Josh at several stages of his life. 

(talking indistinctly)

 Oh, did it? There it is, all right. So that's Josh as a young photographer, I take it here in Madison. Here he is at Cold Spring Harbor with, this is Sewell Wright, who is a famous geneticist, one of the three fathers of population genetics. 

He was a member of our faculty for many years here at the University of Wisconsin. He had been a faculty member at Chicago. Then when he reached the mandatory retirement age at Chicago, which was 65, we hired him here. He could work for five years here before he reached our mandatory retirement age. He died at the age of 99. He was still working and still writing papers. He would still be doing that if he hadn't fallen and broken his hip. This is Josh. This is Walter Burdette, who I won't go into. But there's a picture of Josh, more or less as he looked the last time he came to visit here and give a lecture in Wisconsin. 

Jim. 

- This is going to be embarrassingly personal... 
(no audio)

Is this better? Well, I think I turned it on. Yes, it says it's on. All right. I'll talk louder. As I say, this is going to be embarrassingly personal, because I want to talk almost entirely about personal relationships with Joshua Lederberg. In 1946, I was teaching at Dartmouth College. 

And I read an article in "Nature" by Tatum and Lederberg. I'd never heard of Lederberg, but everybody knew about Tatum. And so, can you hear me in the back of the room? Good. No? 

(laughter)

 I heard one no, so I'll speak a little louder, or try to. And it was a paper reporting recombination of bacteria. And what he did was set up circumstances such that when he put two parents into a culture medium, neither parent would grow. But if there were recombinant type, involving the right genes from both parents, they would grow. 

So it's a little bit like finding a needle in a haystack, by burning down the haystack. Or a better analogy would be getting the needle to grow while the haystack didn't. Anyhow, that just proved once and for all that there was such a thing as sex in bacteria. I had not met him at that time, of course. Then the next summer, 1947, I decided, as many people did, that maybe nucleic acid was going to be important. And so I went to a conference on nucleic acid at Cold Spring Harbor. Lederberg was there, too. He wasn't on the program, but many people wanted to know what he had been doing. So we had an evening session. And he talked at least two hours, maybe longer. 

But for me, the time whizzed by, I was so excited about what he said. And I remember vividly, at the end of his talk, I asked a question which showed I understood some of it, which I don't think was true of many of the audiences. They were mostly chemists and worked with the genetic techniques he was dealing with. Anyhow, that got us acquainted. And we spent quite a bit of time talking at Cold Spring Harbor that summer. He knew by then that he was coming to Wisconsin. And he knew that I was interested in teaching. And he was trying to learn to be a teacher, so we talked a bit about teaching methods. Then later on that same summer, there was a meeting at Woods Hollow, a biometrics society, and I went to it. He turned up there, too. 

So again, we spent some time together. The most memorable time was Ari Fischer's lecture, in which he was describing a model for recombination. And instead of taking into account that the four strands, Fischer considered only two. And Joshua and I discussed how curious this was, that Fischer wouldn't know more about myosis than that. But he had the courage to ask the question, I didn't. And Fischer said, young man, this is not a two strand model, it's a one strand model. So to Fischer, the only problem was, given the past, given the offspring, everything in between is a black box, and we don't care about it. 

(light laughter)

 Anyhow, that threw Josh and me still closer together. And the next thing I heard was an invitation to be considered for a job at Wisconsin. 

That was in the fall of '47. They said that Josh did this, and I hadn't the slightest doubt that he did, but I have no proof of it, or disproof either. So I went here at Christmastime to be interviewed. I met with the then Dean at the College of Agriculture. He asked me if I'd ever lived on a farm. And I had. So I answered that question well, and it improved my standing. He said since I lived on a farm, I could identify better with farm students, and otherwise. So I went back and met Josh, who had had an interview with the same Dean the year before. And he asked him the same question. 

And his response was something like the fact that he never saw grass till he was 20 years old, or something. 

(laughter)

 But they hired him anyhow. An interesting side light about that trip. I came on a train from Chicago, and there were two train stations in Madison, both of which arrived at noon on the same day. I didn't realize there were two of them. So I had to be met twice by two different groups of people, who didn't know which train I'd be on. One of the most impressive things from that visit for me, were the appalling circumstances under which Lederberg was working. He was in a room about 15-foot square. He had himself, his wife and two or three dish washers, and the one graduate student, I think Norton Zinder was here by that time. 

And I was just astonished that here was this world shaking research going on in a laboratory that most people wouldn't be found dead in, if they could help it. Anyhow, he got the work done. The next thing I knew, I was offered the job here, and came the next summer. Then I saw Joshua every day, or practically every day. And we became the closest of friends. I was his closest friend and he was my closest friend for the period of time when he was here. We never did work in the same area. We sort of studiously avoided that. But we maintained deep interest in what each other was doing. The early work that he did, it blossomed very rapidly, and one of the first things to be discovered was a factor, an episode as we now call it, which determined sex. 

So there was such a thing as maleness and femaleness. But one of the things that made me realize is what a lucky experiment his first experiment had been, because it worked. If you take two random strains of bacteria, the chances of them being opposite mating type is very, very small. He was just very lucky. Furthermore, he wasn't prepared to do very many experiments. He said if the first experiment didn't work, he was going to give up. Fortunately, it did work. And so, therefore, the nation has one less surgeon and one more geneticist as a result of this. He discovered finally, that this sex determinate factor could land on a chromosome and behave like chromosomal sex determination. He discovered transduction, as Millard has mentioned. 

But most of the emphasis in the early years was on chromosome mapping. And he was trying to map the genes on a chromosome, by analogy, with the processes that were used in other higher organisms. And part of the time it worked, but much of the time it didn't. We know the answer now. A bacterial chromosome is a circle. And they didn't fit any kind of a model that a linear chromosome, which he tried to fit everything to. I learned later on about Lederberg's appointment here at the University. And it was a near thing. There was considerable opposition to him. Partly because he was here to teach in the College of Agriculture. 

And people wondered what a city boy, who worked on conjugation of bacteria would have to do with the price of milk, and all the things that we were supposed to be concerned with in agriculture. So it was quite hard getting him hired. And RA Brink deserves the credit for pushing this through the department. By the time I got here, one of the faculty members said he wanted to say that although he had opposed Lederberg, well, he'd been here for a year, and they'd discovered how good Lederberg was. He was sorry he'd opposed him. That was probably everybody's view. The other thing about this that I found interesting then, and look back on with some amusement now, the general reaction to this discovery that bacteria has sex was to say, how cute. These little organisms to the same things we do. Or, in the College of Agriculture, these things do the same things that cattle do. But the point is that it's curious and it's interesting, but the real point is that most of us, and I'm including myself for a while, didn't realize that this was the most promising way we had of really getting at the elusive nature of the gene, which of course, was the central question in genetics at that time. 

And this offered the chance of resolving the distances, measuring distances, to such smaller dimensions that they would be like a gene, and we had a good chance of having something to do with the structure. And that turned out to be the case. It was about five or six years later that Watson and Crick discovered the structure of DNA. Incidentally, in 1947 at the Cold Spring Harbor Symposium, there was considerable data at that time about whether the gene was DNA, or protein, or some mixture of both. And I remember there were a few jokes about the possibly it may just turn out to be DNA after all. The reason was that perhaps the more intelligent you were, the less likely you were to be correct on this issue, because everybody had the wrong picture of the structure of DNA. The structure as it was thought of at that time. There were known to be these four components. And it was just thought that the same four would repeat all the way along the long molecule. There's not much basis for genetic variability in an identical set of objects. 

So, most of the people, for that reason alone, I think, dismissed DNA as the likely genetic control. Another reason was that the most influential person, in later years argued for proteins, was man named --. He argued that the experiments Millard talked about-- transforming principles, he kept saying that even though we had purified it, it was 95% DNA, 5% protein was important. Then he transferred the data to 99% DNA and he said protein's powerful stuff. And I don't think he ever really was convinced till quite a bit later, actually. I want to say just a few things about Lederberg himself. He was the most intelligent person that I've ever had contact with on a day to day basis. It seems that whatever anybody knew, he knew more. And some people found that disconcerting. I thought it --. 

But there were people who were made uncomfortable by this, particularly people in other departments who knew that Lederberg knew more about their field than they did. And I can understand this feeling. I took advantage of it. Not really in a conscious way, but the effect was the same. I would tell him something. I'd forget it, he'd remember it. And so in effect, I could file information with him. 

(laughter)

 And have it stored and recited back to me, usually in refined form. And I remember one, I'll cite one of the most spectacular times. 

I hardly ever knew something that he didn't, but once in a while. And one of these was a chromosome mapping function, a little algebraic trick involved in deriving it. So, I showed him how to derive this thing. And then, that was all of that conversation at the time. Then about a year later, at least a year later, I was in my office working away on this. And I tried to re-derive it, and I'd forgotten how. And Josh breezed in, just as he often did, just wanted to gossip. And so I showed him this problem and he straightened me out. And I don't think he gave it any thought during that whole years’ time. And similar things happened several times. 

When he left, I missed this encyclopedic, this walking encyclopedia that I could use. He also had a sense of humor. And I'll mention just one example of that. I discovered to my pride, really, that I'm a survivor of the 1918 flu epidemic, and that I have the antibodies for that original virus. So I sent him an email and said that I'd discovered that I really carry this, and it's just possible that I have little fragments of the virus myself, and it might be useful for science. He wrote back and said, "I don't think you're worth much. If you'd been frozen, you might be." One more thing. It's still highly personal. But on one evening, he called me up and asked if I would come over to his house that night. 

And I didn't want to. I had something else I wanted to do that evening, but he seemed much more urgent than usual. So I just gave up, got out of my other plans and went over and spent the evening with him. And the explanation for all this, is that he had heard that he was going to get the Nobel Prize. And he wanted to share it with someone. So he and I and Esther shared the celebration of his winning the Nobel Prize. Not a drop of champagne. I don't remember what we had to drink, but it was a joyous occasion, of course. I remember discussing with him what he thought about getting the prize at such an early age. Did he think he didn't deserve it, possibly. 

He said, no, he thought he deserved it all right. 

(laughter)

 But he was a little taken aback by how soon it came, too. Later on, after he moved from here to Stanford, one other thing. It was a sad day in my life when he left here to go to Stanford, because I wanted him to stay. But as an inducement to him, and clearly that's the reason they did it, they offered a package deal to me too. So I could've gone with him to Stanford, and thought really seriously about it. That's the only time I've ever seriously considered leaving the university. But I had family ties here, and my wife didn't want to move. We had three children who were very much tied here. 

And I'd been influential in tracking -- in this state, so I decided I not only must, but really wanted to stay. So, we separated at that time. And although we stayed in touch reasonably well, I saw him only a few times. The most recent was about a year before his death. And it was a little bit of a sad occasion. It was a dinner at his house. Usually, in earlier years, whenever there was any kind of a party of any sort, he largely dominated the situation. Everyone wanted to hear what he had to say. It was quite different this time. He was reserved and quiet. 

He knew what was going on and contributed to it. He didn't take the kind of initiative that he ordinarily did. In fact, I did. And people were paying more attention to him than to me, which had never happened in the past. I said that backwards. That goes with the territory at my age! One other thing that interested me. At this time, while Josh was still here, Carl Sagan lived in Madison. And at that time, he wasn't famous. In fact, he was quite shy. 

But he and I talked a great deal. And we were interested in some similar mathematical problems. And one day he came in with an idea. And I think the idea was essentially, that the surface of Mars, or the moon, I can't remember which it was at the time. But the surface would be less interesting than digging down below the surface, because if there had been life in the past, maybe it would be buried. Maybe the geology of the moon would be more interesting than the geography of the moon. I thought that was a good idea, so I said go in and tell him, he's next door. And Sagan said he was too afraid to go in and talk to Lederberg, he's famous, and he might bite my head off. So we arranged for a little evening meeting with the two of us, and two or three other people. And Carl Sagan had planned very carefully what he was going to say. 

He had points 1, 2, 3, for which he could deduce atom A and atom B. He went through points 1 and 2, and Lederberg said yes, and from that it follows point 3 and atoms A and B. And the whole discussion was over in less time than it's taken me to describe it. And so there wasn't much of a discussion that evening. We had all small talk after that, and that was the end of it. But it was a happy ending. Later on, Lederberg took Sagan on to join him at the Department of Genetics at Stanford. Sagan used to brag about the fact that he was the only astronomer who had a professorship in a genetics department. One other things was computers. We had a course in computer software for faculty members. 

He and I both took the course. And in those days, programming consisted of actually physically picking up wires. It was like an old-fashioned telephone switchboard. And you had certain ways of routing things, and so on. So we gave them an illustration of booleanology, and very little more. Anyhow, I didn't like it and dropped out after the course was over, but Josh loved it. And it was very obvious that computers were going to be a big part of his life, and a major reason for leaving Wisconsin, whereas the greater opportunity for gearing his life around computers if he went to Stanford. So I'll turn it back to Millard. 

(applause)

 Thank you. 

- I've also-- 
(audio feedback)

You should've had this microphone! In talking about Joshua's prodigious brain, people used to talk about his amazing ability to read things, almost at the speed of light. And I had one colleague here who remembered going in to talk to Josh, and asking him some fairly detailed questions about science. And while they were talking, he was reading a scientific journal. And he was more or less reading it like that. 

(light laughter)

 He finally asked him, you know, a question about the paper that he was flipping through. And it turned out that Josh in fact had been reading paper while talking to him. 

He seemed not only to be reading it, but actually he had understood it in detail. And Jim said that he'd had a similar experience. He went in to ask Josh a question about a paper that he found challenging. He gave it to Josh and Josh flipped through it and Jim said, well, I'll give you a little while to read it and I'll come back and talk about it. And Josh said I've read it and I'm ready to talk about it. As I said, I'll try to teach you a little bit of science about what Josh did. When Josh first got interested in bacterial genetics, he was actually trying to do something that was called transformation. And transformation had been discovered just a couple years before Josh had starting doing his experiments, by Oswald Avery and his colleagues in the bacteria Pneumococcus. And I have drawn a cartoon of Pneumococcus here, two Pneumococci with different surface structures on them. This is what distinguish Pneumococci. 

And Avery had discovered that if you extracted DNA from a bacterium that had this kind of surface on it, and you just took the DNA and added it to a culture of Pneumococci that looked like that, so you start out with that kind of Pneumococcus and you add some DNA to it, that most of the bacteria that came out of that culture were just like it, like this original strain. But some of them, as a result of being able to take out genetic information in the form of extracting DNA from strain A, would take on the properties of strain A. This was the first evidence that the genetic material was DNA. And Avery got credit for having contributed this piece of knowledge. But at the time, bacteriologists were kind of dubious about bacteria having genes at all. And for some reason, they seemed to think that bacteria were too small to have genes. Their logic isn't quite clear, but that's what many bacteriologists thought. And they thought that the way in which bacteria dealt with the world around them was more a matter of sort of trial and error and learning how to get along in an environment than actually inheriting something from their parents when the cells divided. So Josh was trying to do an experiment like that. And then he decided that he would just mix together bacteria, cultures of bacteria, without extracting DNA, and see what happens. 

And he wanted a powerful way to identify recombinant bacteria, bacteria that had properties of both parents. He started off with E. coli, a bacterium that's a rod shaped thing like this. It can grow in a minimal medium. What that means is it's a medium that contains just cells in some simple energy source, like sugar, glucose. And in a medium like that, the bacteria can make all the biochemicals they need. They don't require the addition of any vitamins, any amino acids, any complicated biochemical materials. Just glucose will do. And they can carry it from there. Josh isolated a mutant bacteria that couldn't grow in minimal medium anymore. 

And he isolated two kinds of deficient bacteria. They were bacteria that were called B- M- bacteria, that would only grow if you added the vitamin biotin and the amino acid methionine to the medium. Then, if you added those two additions to the ordinary minimum medium, salts plus glucose, the bacteria could grow. He wanted to make double mutants like this, that required both biotin and methionine, because if you just had a bacterium that required one thing, like biotin, then it might be that when you looked for something that was able to grow without the addition of biotin, that some sort of reverse change could take place, a mutation, that genetic mutation, that would make the biotin requiring bacterium independent of biotin. He wanted to make sure that the parents used in this cross were just unable to get back to the completely wildtype, the type that could grow in minimal medium all by itself. So he figured that if he had two mutations in the bacterium, that whereas a bacterium that required only biotin could go back to the biotin independent type at perhaps a frequency of one in a million cells, that if he had one that required two things added to the medium, that only a millionth of a millionth of the population, or ten to the minus 12, would be able to revert to grow in minimal mediums, the condition that's called prototrophy. And a millionth of a millionth, that's a trillionth. That used to be a big number. 

(laughter)

 But anyway, it's a big number relative to the size of bacteria populations, so you don't get back to wildtype very easily from a double mutation like this. 

Then he isolated another double mutant that required threonine and an amino acid named leucine, in order to be able to grow. Then he mixed those two bacteria, the one that required biotin and methionine, and the one that required threonine and leucine, he put them in a medium that had everything in it, so that they could grow up into a large population. And then after they had grown together, and he had some ten million cells, or so, then he looked to see whether there were any cells in that population that were able to grow in minimal medium. And he found that yes, there were. When he grew them separately, he didn't find any cells that could grow in minimal medium. But when he grew them together, there were cells there that could. That was evidence that these bacteria had interacted to produce cells that were once again just like the original non-mutant parent strain that could grow on minimal medium with now biotin, methionine, threonine, or leucine added. It was a lucky thing that he made these double mutants, because as I said, individually, these cells can revert to the wildtype with just one mutation at about a frequency of one in a million. He found that his cells, one in ten to a hundred million of this mixture of cells, was capable of growing like that. So he got a very significant increase in the number of cells by growing the cells together, the number of recombinant cells. 

The first demonstration that bacteria were capable of cooperating to produce recombinants that had genetic properties of both parents. The question arose, was this actually a result of an interaction between these two bacteria to produce this recombinant type. Did somehow the threonine, the TL+ from this bacterium and the BM+ from this bacterium get together through physical contact between these two bacteria, or perhaps was it just the transfer of loose DNA from bacteria of one sort of popping and being taken up by the other bacteria that led to this genetic transfer. They did an experiment, rather Bernard Davis did an experiment, to answer that question, to show that in fact, the two cells had to have physical contact with one another. He grew a parent A, in one side of a U-shaped test tube, and parent B in the other side of a U-shaped test tube, and put a filter in the middle of this tube that was small enough to allow DNA to travel from one side to the other, but not to allow bacteria to travel from one side to the other. And under these conditions, he found no recombinants between Lederberg's two strains of bacteria. He could slosh the broth in which the bacteria were grown back and forth, presumably forcing DNA from one side to the other. But he never found any bacteria on either side that were capable of growing without nutritional supplement. And so it was demonstrated that physical contact between the bacteria was needed for recombination to take place. This convinced Josh that the bacteria were somehow fusing, as if they were an egg and a sperm, forming new little bacterium that contained the genomes of both, and then dividing to give rise to recombinant offspring. 

That turned out to be wrong. The bacteria do have to touch one another in order for this process of conjugation to take place. I want to tell you about one other experiment that Lederberg, Josh and Esther did. Another thing that he did, in addition to discovering sex in bacteria, was to ask a question that was important from the point of view of people interested in the theory of evolution. The question is, when you take a bacterium that is sensitive to an antibiotic, and you put it into a medium containing the antibiotic, and you find that a very small number of antibiotic resistant bacteria grow up in the presence of this selective agent, this poisonous chemical, does the poisonous chemical cause the bacterium to become resistant, or were there resistant bacteria present there before the poison was added. Does an antibiotic teach a bacterium how to be antibiotic resistant, or does the bacterium already know before it's exposed to the antibiotic? The Darwinian idea of evolution is that populations contain genetic variance, and that when you change the environmental conditions of a population, and you change the genes that you find in the organisms as a result of growing them in a new environment, in a selective environment, that the new genes you get were there in the first place. They only increased in frequency as a result of a natural selection resulting from the changes in the environment. And Lederberg wanted to find out whether he could demonstrate that in fact, when you impose selection on bacteria by adding antibiotic, that you are selecting cells that already are resistant and are present in the original population. And that had been tested by a rather sophisticated statistical experiment done by -- a short time before, but people found it so hard to understand the math in that experiment, that they had some doubts about the truth of the discovery. 

So, Joshua and Esther Lederberg went out to do it in a much more straightforward way. Here's what they did. They used the technique that's called replica plating. I'll try to show you how that works. The idea is that if you have-- What I just said was that if you believe that changes in bacteria result as a result of adaptation, then if you have a bacterial plate like this, this is a petri dish, covered with colonies of bacteria, each one of these colonies grew up from one bacterium. If the production of antibiotic resistance bacteria requires the presence of an antibiotic, then a plate like this, that contains little colonies of bacteria, with perhaps a couple million bacteria in each one of these colonies will contain no cells that are resistant to the antibiotic. And only after you expose those cells to the antibiotic, would you have any resistant cells. If mutation is the explanation for the appearance of antibiotic resistant mutants, then if you could look down at these colonies that actually identify antibiotic resistant bacteria, you would find that a bunch of bacteria growing on a plate like this, with no antibiotic, would after they got to a dense enough population, contain some mutations. There would be some colonies that contain just one bacterium that was resistant. There would be some colonies that would contain two, that had resulted from one mutational event that then gave rise to a bacterium that doubled and gave rise to two resistant offspring, so they're heritable changes. 

There would be a small number of colonies that contain four bacteria, in which the cell that was originally mutant, that appeared during the growth of the colony had doubled twice. There would even be some that had eight. And actually, if you could do this experiment, if you could go back and look at these colonies, you'd find that there's be half as many colonies with two cells as there were with one, and half as many with four resistants as there were with two. I'll let you figure that out yourself, but that has to do with the doubling of the population every time the cells divide to form a colony of a million cells from one original cell planted on the plate. So Josh and Esther said, okay, well the troll for us is to try to demonstrate that there are bacteria present in colonies that have never been exposed to antibiotics. And they used a technique called replica plating, which looks like this. You start off with a culture of bacteria in a petri dish. No antibiotic in the petri dish. And you add some of these bacteria to this petri dish. You take a glass spreader and you spread the bacteria over the surface of the petri dish. 

And then you let the bacteria grow up so that there are colonies on the surface of the dish. And each of these colonies is the offspring of the original bacterium spread on the surface of that dish. That comes from a population that are not antibiotic resistant. So the original plate, right after you've spread stuff on it looks like this. The bacteria are too small too see. After you incubate it overnight, it looks like this. It has colonies growing on it. And what Josh and Esther did was to start off with a plate like that that had colonies growing on it. And they made a sampler that was just a block of wood. This is a cylinder of wood, covered on one side with sterile velvet. 

And this is just like having a zillion little needles sticking out of the surface of this sterile velvet. And they pressed that velvet down onto the surface of this petri dish, and it would take up a sample of the bacteria on the surface. Then they could use that as a stamp, to stamp a sample of the bacteria from the original dish onto several successive petri dishes containing the medium with antibiotic added to it. Then after they incubated these cells overnight, they would find-- Here's the original plate, the master plate that has a lot of colonies on it. Here are the antibiotic containing plates. And they have a few colonies growing on them. They can compare the positions of these colonies to the colonies growing on the original plate. And in this set of replica plates that have been stamped from the velvet, here's one colony that's present on the original, it's present on two of the replica plates. Here's one that's present on one, two, three of the replica plates. Here's one on three replica plates, that one there. 

There are some colonies that only appear on one of the replica plates. But these guys that appear on identical positions on two or three successive plates, must come from colonies here that contain several bacteria, a little clutch of bacteria all coming from the division of one mutant cell. So if you look back to the original plate, and you isolated the bacteria from this spot, and isolated the bacteria from this spot, this spot, you might find that there were cells here that were antibiotic resistant that came from the same mutational event as the cells here in the replicas. And that's what Josh and Esther did. They went back to the original plate. They isolated bacteria and they tested the bacteria individually, to see whether they were resistant to antibiotics. And sure enough, they managed to isolate cultures of pure bacteria resistant to antibiotic, that had never been exposed to antibiotic themselves. So they demonstrated that it was possible for bacterium, without exposure to a selective agent, to mutate to resistance to that selective agent. This was a masterful experiment, and became very famous. And furthermore, the replica plating technique using the velvet to stamp bacteria from one plate to another was so useful that it's been, it's still used every day in labs around the world. 

Whoops, I don't think that's what I intended to do. Anyway, that's all I have to say. That's the science lesson. 

(applause)

- I have one addendum to this. I was very much involved in discussions with this experiment... 

- Yes, turn your mic on. I have to undress to get my microphone! 

(laughter)

- I was very much involved in the experiment. It occurred to me, and I finally put it in a paper, this is no different than selecting for milk production in bulls. You, of course, can't test milk production in bulls, but you can examine their female relatives, and then infer what the bull's composition is from that. That's essentially the same as this. You take near relatives of the bacterial cell, test them for the antibiotic. And if they're resistant, then the original cell had that. 

- Was Joshua Lederberg married at the time he did the experiments that won the Nobel Prize? 

- The very first experiment, I think he did before he was married. 

- I think so. 

- By the time I met him in 1947, he was married by that time. So he must have got married in 1946 or early '47. 

- I think he did the experiments on showing that there was sexual recombination in bacteria before he was married. All the rest of this stuff, the discovery of transduction, the discovery of this wonderful replica plating technique was done after he was married. 

(inaudible)

- Millard, could you repeat the question, please? 

- The question is, have there been people who have suggested that his wife was much more involved in Josh's major discoveries than she's given credit for. They are both gone now, so it's difficult to go back and quiz them on the subject. 

- That doesn't keep me from having an opinion. 

(laughter)

- What's your opinion? 

- My opinion is that virtually all the ideas came from Josh. He was a genius. She was just a very good everyday scientist. By ordinary standards, she was fine. But his standards, she wasn't. And the particular experiment that was much discussed is this replica plating experiment. And I think she had to do with the selecting of the velvet. 

But certainly, the idea was his, because we talked about it, he and I. She wasn't involved in any of those discussions. 

- I have a question. Since you're talking about family, and he was a genius in many ways, what about their children? 

- Most geniuses have children who are not geniuses. 

- What about their children? 

- They were all of average intelligence. They are all successful people. He had a brother, who, again, by ordinary standards, an excellent biologist. But again, he's not-- 

- When we spoke about the very small numbers of bacterium resulting in mutations, how do you measure that? How do you find a single bacterium? Is it all inferential statistics, that you kind of work backwards from subsequent generations? 

- Go ahead. 

- You dilute the culture bacteria until you have a countable number of bacteria. You spread that on the plate and you keep track of how much you've diluted the culture, and you calculate back to the original concentration. So you first make one dilution and you plate on a medium that doesn't contain any antibiotic, for example. Then you make a lesser dilution and you plate on a plate more bacteria on a plate that does contain antibiotic, and then you can determine how many cells are antibiotic resistant and how many total are present. So it's just a matter of doing a little multiplication. 

- Let me say one thing. 

This wasn't the question, I'm following the tactic of some politicians that I've heard of, and not answering the question. But I want to answer a slightly different question. He finally did devise a way of distinguishing between a mating pair of bacteria and a pair of bacteria that had just separated by ordinary division. And he found one strain that was big, relatively fat, and another strain that was small with a long tail. When these two mated, you saw a little tadpole like organism. That could be seen, even if they're only a tiny fraction of a percent of them. Later on, what was earlier just inferential, actually you could see physically. 

- Jim mentioned that one of the things that was discovered in the Lederberg lab, and I don't know whether it was Lederberg or Cavalli, or who it was, but it was this factor that makes bacteria male. And it turns out that this is a little extra circle of DNA that's in the bacterial cell. It's not part of the bacterial chromosome and it isn't necessary for bacterial growth, so you can take it out and the bacterium is just fine. 

You put it in and the bacterium becomes a male bacterium capable of transferring genes to a female bacterium. And it also transfers this little F factor, so maleness in bacteria is a disease. It's an infectious condition. 

(laughter)

 So you can add one or two male bacteria to a culture of female bacteria, and maleness spreads through the population until everybody is male. 

- There was a lot of wondering around here at the time, why all bacteria don't become male. It was Cavalli who did this. He was Italian, and then came here to work with Lederberg, and did that while he was here. 

- If Josh Lederberg was intrigued with computers from very early times, how did he end up utilizing computers as they changed so dramatically during his lifetime? 

- They way I see it, he just changed with them. 

I don't know if that's an adequate answer or not, but he certainly kept up with the technology. 

- How did he take advantage of the technology in any particular way? 

- Well, the -- which you mentioned, was entirely computer done. And it was a beautiful piece of stuff, as a matter of fact. He used it for chemical analyses, as Millard said. He also devised a nomenclature system for organic chemistry. I think everybody in the room that took chemistry was frustrated with the fact that there's no unambiguous naming system in chemistry. Joshua thought there should be one. And so with the aid of his computers, and his program, he was able to devise a way of, I remember some of the details, hardly any of them actually. But you start on one end of the problem, the carbon atom, and then you number the atoms. 

That gives you a system for systematically ordering them. And if there's a ring compound, he had procedure for taking that into account. Anyhow, it was unambiguous. And the surprising thing to me was I would have thought that would've instantly catch on with organic chemists. As far as I know it hasn't caught on at all. I don't know if anybody pays any attention to it. 

- There was one point right after he left here and went to Stanford when he was, that was still in the days that computers were run with punch cards. He was carrying around a pocketful of punch cards. And as bright ideas would occur to him, he would write them down on his punch card. Then at the end of the day, he'd give all of his bright ideas to the secretary to punch into the card, so that he had a file. 

Despite his prodigious memory, he wanted a file of his bright ideas that could be sorted into bright ideas pertaining to the given fields. 

- You know, the other thing, Tom, that he said while he was still here, is that he'd like to gear his whole life around computers. So the computer, he didn't make any distinction between his personal life and his scientific life. It was all interwoven and indexed. 

- Question. 

- We heard about experiments with antibiotic resistance, and we heard about recombination sex in bacteria. So did Lederberg, at that time, ever put the two together and think about sex in bacteria in an evolutionary context? 

- He did. I was very interested in the evolution of these things at the time. So we tried to get him interested in it. 

He thought these were premature questions, and that we better learn about them more first. And of course, he was a believer in evolution and interested in evolutionary processes. He didn't spend very much time and research on evolutionary questions. So, much to my dismay, I wanted to talk about evolution and he didn't. 

- So we'll have to have Jim back to talk about "why sex," because he's thought more about that subject than Lederberg did. 

- You have two key pieces of evidence, and if you put them together, that's a whole big story. 

- Of course, in a sense, the whole growth of bacterial colonies, this is evolution in miniature. What were you going to ask? 

- I was thinking, among his many unique abilities and talents, his reading ability of pure speed and comprehension, is mind boggling. Now, what I'm wondering, if he were alive today, they would probably hook him up with all kinds of things, burn an image, what's going on in his brain. 

But was it ever studied by any researchers, in terms of that ability? You don't know? 

- I don't know, either. Except I do know that psychologists have a field day speculating about that. 

- That's what I mean. 

- I'll say something mildly disrespectful about Josh. Because he was that kind of reader, he thought that he could give a seminar on his life in science, for example, by getting an overhead projector and putting down photographs, or the first page of each of the articles he'd written, flash them on the screen for two or three minutes, and then whip them away and put down another article. He'd say very little about what was in that paper. And of course, nobody in the audience could do what Josh could do, so it made that kind of seminar absolutely dazzling. All you could do was sit there and wonder, what does he think he's doing. 

- For somebody so brilliant, he seemed to give some of the lousiest talks. 

(laughter)

- Did he have any other extraordinary capabilities, musical for example? 

- I don't think so. I don't think he had any particular appreciation for poetry or anything. It seems to me, Tom, that as I think of other geniuses in the genetics world, I like to compare Haldane and Ari Fischer. Haldane had a very powerful mind, something like Lederberg's really. And he learned everything and worked math problems very rapidly. But I've had the impression with Haldane's work that if I just took ten times as long as he did, or hundred times, I could do it. 

But with Ari Fischer, though, he just had ideas out of nowhere. And I think there's a distinction between creativity and power. And Lederberg himself said he didn't think of himself as creative. He thought of himself as having a better, just more power than most minds. And I think that's a correct diagnosis. 

- I heard earlier today that lambda phage was discovered in the Lederberg lab. Is that correct? And if so, can you tell a little story of one of the most famous viruses that I know of. I didn't realize that it was discovered across the street. 

- That's one of the things for which Esther does deserve some credit. 

She did most of the early work on that. 

- Do you all know what a phage is? There are viruses that grow on bacteria. And they are called bacteriophages, or phages for short. And some of those viruses can just enter into the chromosome of the bacterium. They infect the bacterium. They insert their DNA. And the DNA becomes part of the genetic apparatus of the bacterium. The bacterium doesn't die. It just divides and gives rise to offspring. 

And all of the offspring have within their chromosomal structure, a virus that, at any time, and usually it's a time when the environment is somehow hostile, for example, in the presence of ultraviolet light, or high temperature, or starvation conditions, or something like that, the virus pops out and pops open the cell and releases a couple of hundred offspring viruses, going out and looking for other bacteria. One of the bacteria that was very famous, of that type, that can enter into a bacterium and grow internally was a bacteriophage called lambda. And it was discovered here in Josh's lab by Esther. And it's a virus that can do transduction. It can pick up a gene from a host bacterium and transfer it to a recipient bacterium. It has many wonderful properties that make it interesting to geneticists. 

- There was a man who was a graduate student at Cal Tech. And I wanted the department to hire him. He worked on Lambda. But they wouldn't do it. 

And the reason given was that we already had one person working on Lambda, and the organism was too small to have two people. 

(laughter)

- Other questions? 

- Is this the work that led scientists to get genetic material from bacteria into plant cells? 

- Well, it's very similar. All of these, it was one of the first steps in understanding how that process takes place. That's another bacterium that grows on plant cells and that inserts genetic information into the plant. And you can engineer bacteria that will insert genes into the plant for you. But it's a very similar process to the process by which bacteria use viruses to transfer genes from one strain to another. 

- Any other questions? Did you have a question? Any other questions? I guess not. Thank you very much. 

(applause)