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Solving the Puzzle (Part 2 of 10)

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A new understanding of life on Earth has forced us to redraw the tree of life. Dr. Carl Woese and Norman Pace describe the process and challenges of categorizing microbial life.

Transcript

 

{Title: Solving the Puzzle}

Narrator, Lillian Lehman: In the Nineteen sixties, most scientists believed that creating a new Tree of Life, by comparing the DNA of different species was impossible, but in Urbana, Illinois, Carl Woese, a jazz aficionado, and molecular biologist, disagreed.

Scientist, Carl Woese: You have to hear the tune, as it were. You got to have an ear, you got to pick up on these faint tones, and if you like them, you go to where you can hear them better. You have to have your own particular sensitivity to the world, and there has to be parts of it that are beautiful to you, because they are beautiful to you, regardless of what anyone else ever thinks. And you see this all the time in a artist, and you see it also in good scientists.

Narrator, Lillian Lehman: For Woese, creating a tree that showed how life on Earth evolved from the first form of life, to the last, became an obsession.

Scientist, Carl Woese: I knew that this was a jigsaw puzzle that had to be put together. Now, in my case, I emphasize, had to be. Because I understood that to really be a biologist to really understand biology you had to understand where everything came from.

{Music plays, "Maple Leaf Rag".}

Narrator, Lillian Lehman: Woese focused first on the evolution Of the first forms of life, microbes. The problem that had stumped everyone else, was that with microbes, you can't tell much about how closely they're related by just looking at them. But Carl Woese had an ace in the hole, a special chain of genetic material, special because it exists in very similar form inside every living thing. Woese began by cutting one of these special chains into sections short enough to manage. Next he took pictures of the sections, using x-ray film. Then Woese began the incredibly challenging task of figuring out in which sequence the four chemicals called A, C, G, and U, were ordered in each section of the chain. Why go to such extraordinary lengths? Because Woese believed that the special chain could reveal how life on Earth evolved. He knew that this chain has done its job so well, that it has been passed down from the first forms of life, to all life that followed. Every bacterium on Earth today has inherited it, and so have you. It was like discovering that all the music ever written, has a few notes remaining from the first piece of music ever created. Woese realized that by comparing the thousands Of A's, C's, G's and U's in the chains of two different species, he would be able to see exactly how much of the score of this special chain, they had in common. The more of the score, that any two species had in common, the more closely related, Woese believed, they had to be on the Tree of Life.

Scientist, Carl Woese: And it was indeed just like putting a jigsaw puzzle together. You don't know what the picture is, and then you put all these little islands together, and you say, oh here's a part of it.

Narrator, Lillian Lehman: Fellow molecular biologist Norman Pace worked up the hall from Woese, during the years he was attempting a new Tree of Life.

Scientist, Norman Pace: I think the remarkable thing about the Woese endeavor, was that it essentially single handed. When ever you go in high powered lab today, what you see is many people bustling around, it was never like that in Woese's lab, it was always just Woese.

Scientist, Carl Woese: You, got up in the morning, ate breakfast, and came into the lab. And then you put these silly x-rays up on your wall, and you looked intensely, but you had to be intense to get through this task. This happens on Monday, Tuesday, Wednesday, Thursday, Friday, and week after week, and ultimately year, after year. I would finish the day, having looked at these films for many, many hours, and I would go home and say to myself, you know you have destroyed your mind again today. And that is how it felt. Everything was dulled down, all that mental energy was used up.

Scientist, Norman Pace: I'm not sure anybody except Carl Woese could have pulled off the articulation of the big tree. It required with drawing himself literally, with drawing himself from scientific society.

Narrator, Lillian Lehman: One key to Woese's approach was to search for the places where major new branches of life began, by looking for the place where a group of A's, C's, G's and U's Showed up in an order he'd never seen before. It was like only having heard notes arranged to play classical music your whole life. {Classical music playing.} And then suddenly hearing them arranged in a rhythm and blues beat. {Rhythm and blues music playing.} And slowly but surely, one after another, the major branchings on the tree began to appear.

Scientist, Carl Woese: You could feel the thing growing. The islands became joined, became bigger islands. And then all of a sudden you see, this is what the picture is going to be about, and you gleefully throw in all of the other pieces as fast as you can.

Narrator, Lillian Lehman: After more than ten years, Carl Woese completed the puzzle. A new Tree of Life created by comparing the genetic make up of different species. When it comes to the branch of the tree that happens to include us human beings, Woese's tree points to a new, very different way of looking at ourselves. The new tree is based exclusively on how similar the genetic instructions of different species are, and the fact is that just like the scores of country songs {Country and western music plays} are remarkably similar to the scores of rock and roll songs. {Rock and roll music plays.} The scores of plants are stunningly similar to the scores of animals, and human beings. And so the Woese tree, far from being just two branches divided between animals and plants, has only allotted animals and plants tiny twigs together, out on the end of the branch we share with all other visible life.

Scientist, Carl Woese: It's difficult to see this tree here as your relative. Because ever since recorded history, almost, mankind is distinguished between animals and plants. These were the two great forms of life, and they were as different as different could be. {Sound of sheep baaing.} But yet, scientists began to find out that there was a lot of commonality between plants and us, and that's the thing that has really shocked even me To find out not how different animals and plants are, but how much alike they are.

Narrator, Lillian Lehman: If you have a hard time believing that animals and plants are alike, consider what it takes to be different. When Woese decoded the scores of a newly discovered group of microbes, including a species that eats volcanic gases in the ocean, he found the letters arranged in a pattern far, far different than any he'd seen before.
It was as if Woese had discovered a new kind of music that human beings had never heard before. Woese found the same unusual pattern in some of the microbes that Karl Stetter had collected from hot springs. Woese realized that their unusual genetic material made these strange organisms so different from the bacterial branch, and from our branch that they had to be given their own branch on the Tree of Life, which he named the Archaea, for ancient. Woese's work was especially meaningful to Karl Stetter. For it shows that the ancestors of all three branches of the tree lived in boiling water. Today most scientist agree with the portrayal of early life.

Scientist, Karl Stetter: Due to the work done by Carl Woese, you can find out where these little tiny bugs are in the Tree of Life, and so it was so interesting. The hotter the temperature, the deeper the branches are, and this makes my work even more exciting.

Narrator, Lillian Lehman: For many scientists Woese's tree has made the case for the scientific view of evolution, more compelling then ever before.

Scientist, Norman Pace: I believe Carl Woese has done more for biology then anyone since Darwin. Always, before evolution had been theories, evolution had been notions, ideas, hypothesis, but as the molecular tree began to spin out, it was very clear that this was not theory. This was fact.

Scientist, Carl Woese: Ever since I was a kid, I've wanted, not only, to understand superficially but I wanted to understand them deeply. I need the truth. Some call this the search for god, and some don't, but you want to go deep, and you want to feel the truth. And priests do this, and many scientist do this.

Narrator, Lillian Lehman: Woese's work made it possible, for the first time, for scientists to systematically explore the invisible world that surrounds us. Now they could begin begin to ask, who lives here, who are their relatives, and what are they doing? There was just one problem, scientists could only ask those questions about the few microbes that they managed to grow in the lab, and collect DNA from. Then Woese's colleague Norman Pace, made break through of his own. At its heart was the new technology of cloning, which made it possible for Pace to take a single strand of microbe DNA, and clone as many copies of it that he needed. Pace realized that he could now collect microbes from any environment, and make copies of their DNA without ever having to grow them.

Scientist, Norman Pace: My feeling was that for the very first time the door to the natural microbial world was open to us, that for the very first time we could understand what the makeup of the microbial world is. And that is, after all, most of biology.

Narrator, Lillian Lehman: The first place Pace tried out the new technique was a hot spring in Yellowstone National Park. What Pace discovered staggered even him. Yellowstone's hot springs were home to, not just a few other worldly microbes, but to a stunningly complex ecosystem filled with hundreds of different species. And it isn't just hot springs that are teeming with microbes. It is every environment on Earth {Classical music playing.} Now scientists are reading the scores of thousands of previously unknown species of microbes, ushering in a golden age in the study of evolution? And of what the Tree of Life on Earth is really like. Scientists have been surprised not just by how many different kinds of microbes there are, but by discovering that some of those species exist in numbers that rival the number of stars in the universe.

Scientist, Norman Pace: The distribution of life on the planet is very different than we would have thought it, even a decade ago. The estimates are that more than ninety five percent of the biomass in the open ocean is microbial. The deep subsurface, and the basalts of the crust of the Earth are shot through with life. Life is in ice. Life is in waters of boiling temperatures.

Narrator, Lillian Lehman: But why does it matter, that we are surrounded by these tiny living beings? Because it turns out many of them are doing things essential to the survival of life on Earth.

Scientist, Norman Pace: The microbial world is paramount, in the context of maintaining the chemistry of the biosphere. The biosphere is fundamentally chemistry. That chemistry is fundamentally driven by microorganisms.

Scientist, Carl Woese: Why should we care? We can't see these things. Well, let's do a thought experiment, and take these things away. Let's take all the bacteria in the world away. Do you know what's going to happen? All the life that we can see with our naked eyes, all that life is going to disappear in short order. The microbial world is the basis upon which our whole ecosphere rests, and without it there is no multicellular life. And a humbling thought is, if you do the converse and take away all the animals and plants, you will see big adjustments in the bacterial world, but it will still be there, growing happily along and evolving.

Narrator, Lillian Lehman: The message of the work of Carl Woese, and Norm Pace, that microbes play a key role on our planet, could hardly be clearer. But what will happen when we can read the entire score, not just of microbes, but of human beings? How will that change our understanding of our role on the planet?

(Transcript provided by Tyler Anderson)

 

 

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