What is life? For most of the 20th century, this issue did not concern biologists much. Life is a term for poets, not scientists, said synthetic biologist Andrew Ellington in 2008, who began his career by studying how life began. Despite Ellington's words, related areas of origin of life and astrobiology research have renewed their focus on the meaning of life. To recognize another form that life might have taken four billion years ago, or a form that it might have taken on other planets, scientists must understand what it is, in fact, that makes something alive.
Life, however, is a moving target, as philosophers have long noted. Aristotle considered "life" and "living" to be different concepts - the latter, in his case, was a collection of existing creatures that inhabit our world, such as dogs, neighbors and bacteria on the skin. To know life, we must examine the living; but the living is always changing in space and time. In trying to define life, we must consider the life that we know and we do not know. According to origin-of-life researcher Pierre Luigi Luisi from the University of Roma Tre, there is life-as-it-now, life-as-it-could-be-and life-as-it-once-was. These categories point to the dilemma addressed by medieval mystical philosophers. Life, as they noticed, is always much more than living, and for this reason, paradoxically,it will never be available to the living. Because of this gap between real life and possible life, many definitions of life focus on its ability to change and evolve, rather than being limited to defining fixed properties of life.
Can life be created in a laboratory?
In the early 1990s, while advising NASA on the possibilities of life on other planets, biologist Gerald Joyce, currently at the Salk Institute for Biological Research in California, helped develop one of the most widely used definitions of life. It is known as the chemical Darwinian definition: "Life is a self-sustaining chemical system capable of Darwinian evolution." In 2009, after decades of work, Joyce's group published a paper describing an RNA molecule capable of catalyzing its own synthesis reaction to create more copies of its own. This chemical system satisfied Joyce's definition of life. But no one dared to call her alive. The problem is, she wasn’t doing anything new or unusual.
"One day this genome will be able to surprise its creator with a word - a trick or a new step in the game of almost life - that he does not expect to hear," wrote the New York Times about the creation. “If it happened, if it happened to me, I would be happy,” says Dr. Joyce. And he adds: "I do not presume to assert, but it is alive."
Joyce tries to understand life by generating simple living systems in the laboratory. In the process, he and other synthetic biologists embody new species of life in living form. Every attempt to synthesize new life forms points to the fact that there are many more, perhaps infinitely more, possible life forms. Synthetic biologists can change the way life develops, or the abilities it develops. Their work raises new questions about the evolutionary definition of life. How to categorize life that has been changed, that has become a product of an evolutionary tipping point, a product of a break in the evolutionary chain?
The history of synthetic biology's origins goes back to 1977, when Drew Andy, one of the founders of synthetic biology and now professor of bioengineering at Stanford University in California, tried to create a computational model of the simplest life form he could find: the T7 bacteriophage, a virus that infects bacteria. colibacillus. The crystal head on the curved legs of this virus is like a lander that lands on the moon and grabs a bacterial carrier. This bacteriophage is so simple that according to some definitions it cannot even be called alive. (Like all viruses, it relies on the molecular engineering of its host cell to reproduce.) The T7 bacteriophage has 56 genes in total, and Andy thought it would be possible to create a model that takes into account each part of the phage and how these parts work together:an ideal representation that predicts how a phage will change if one of these genes is removed or removed.
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Andy built a series of T7 bacteriophage mutants by systematically knocking out genes or changing their location in the tiny T7 genome. But the mutant phages fit the model for a very short time. The change, which should have led to their weakening, led to the fact that their offspring ruptured E. coli cells twice as fast as before. Didn't work. Eventually, Andy realized, "If we want to model the natural world, we have to rewrite the natural world so that it becomes simulated." Instead of looking for a better map, change the territory. Thus the field of synthetic biology was born. Borrowing methods from programming, Andy began to "refactor" the T7 bacteriophage genome. He created the T7.1 bacteriophage, a life form designed to be easier for the human mind to interpret.
Phage T7.1 is an example of the so-called over-Darwinian life: a life that owes its existence to human design, not natural selection. Bioengineers like Andy view life in two ways: as a physical structure on the one hand, and as an information structure on the other. In theory, the ideal representation of life should activate an invisible transition between information and matter, design and implementation: changing a few letters of DNA on your computer screen, printing an organism according to your design. With this approach, evolution threatens to spoil the engineer's design. Preserving biological design may require that your intended organism cannot reproduce or evolve.
On the contrary, Joyce's desire to be surprised by his molecules suggests that the ability to open evolution - "resourceful, omnipotent, limitless" - is the most important criterion of life. In keeping with this idea, Joyce now defines life as a genetic system that contains more bits of information than the number needed to get it going. But in accordance with this definition, if we take two identical systems with different histories - one designed and the other developed - only the latter will be considered alive; a rationally designed system, regardless of its complexity, will simply be a "technological artifact."
Design and evolution are not always opposed. Many synthetic biology projects use a mixture of rational design and directed evolution: they construct a host of mutant cells - in different versions - and choose the best one. Although Joyce's new view of life includes evolution, it also requires a sudden appearance rather than a long Darwinian development. Emergent life fits into a culture of sudden innovations, ideas of which include the magical appearance of a working bud from a 3D printer. Design and evolution are also compatible if bioengineers see genetic diversity as a treasure trove of design elements for future life forms.
For some synthetic biologists, the path to what mystics call life beyond life - which transcends life as we know it - is through biological engineering. Andy describes his calling in terms of a desire to contribute to life, to spawn new kinds of "incredible models that will flourish and exist." Joyce contrasts life and technology with a fundamental thermodynamic tendency toward disorder and decay. What new forms will life receive? Time will tell.
Ilya Khel