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String theorists and systems biology

At Harvard, former string theorists leave behind quantum mechanics and relativity for genes and cells.

Corinna Wu

In systems biology groups around the world, many physicists have found a new home; they use their computational skills to, for example, build computer models that show how gene networks and cells behave. In Harvard’s systems biology department, even researchers who have studied string theory—a field seemingly distant from biology—are finding their skills in demand. Systems biology offers the big, complex questions that excite people with a theoretical bent.

Take Pedro Bordalo, for instance, who earned his PhD in physics from the University of Paris studying string theory. String theory describes fundamental particles as vibrating strings and offers a way to resolve the incompatibility between quantum mechanics and general relativity. It has been called “the theory of everything,” the theory that underlies all others. In short, it’s about as abstract and mathematical as science can get. “I was happy with my PhD, but for the rest of my life, I wanted to do something else,” Bordalo says.

A turning point came when he attended a biology conference for physicists, at Hebrew University in Jerusalem. He started to look around for labs and contacted biologist Marc Kirschner, the chair of the systems biology department at Harvard. Because systems biology looks at complex biological interactions from a more integrated point of view, Bordalo found that it fit his way of thinking as a physicist. “Conversely,” he says, “it is the place in biology where people are interested in having people [from other disciplines] come over, so it’s a win-win situation.”

Now, as a postdoc in Kirschner’s lab, Bordalo is studying how genetically identical cells exhibit different behaviors that might allow them to compete in or adapt to different environments. He spends about half his time in the lab doing simple experiments and the other half developing computer models to figure out how that behavioral variation comes about.

Hands-on learning

Morten Ernebjerg, another former string theorist in Harvard’s systems biology department, decided late in his graduate studies at Harvard that string theory was a little too specialized for him. “It was work on very small, very hard problems in a small corner of a technical field,” he says. “In the end, it didn’t really suit my personality, what I imagined science for me would be like.”

To explore other fields, Ernebjerg took a summer-school class in France, which had lectures on many topics, including biology. “Somehow that really triggered something in me,” he says. The lectures confirmed his feeling that biology had the same types of big, conceptual challenges and theoretical problems that first attracted him to physics. Now a postdoc with a PhD in physics, Ernebjerg is studying how complex microbial communities in soil work together and survive.

Bordalo and Ernebjerg knew very little biology when they started; they learned on the job and by talking to colleagues. Learning lab work wasn’t hard, says Bordalo, but doing it takes time and is important for theoreticians, especially in the beginning, to learn what is experimentally possible. “The biggest challenge when you change fields is to find out what are the important questions which are interesting and which you can solve,” he says. “It’s often not clear whether experiments you might want to do are possible–in general, they’re not. So you have to be close to people who are actually biologists.”

Flood of physicists

Neither Bordalo nor Ernebjerg applies string theory to his present work. But they both draw on their experiences dealing with abstract concepts and working with large amounts of data—skills that are needed in the field, says Timothy Galitski, a biologist with the Institute for Systems Biology in Seattle who has worked with three physicists in his lab. “We subscribe to the belief that biology is becoming an information science.”

Bordalo says a whole generation of scientists went into string theory because it was exciting and a lot of new work was taking place. Now, the same revolution is happening in biology. “Maybe many people who would have gone into string theory, in the next generation will now go into biology instead,” Bordalo says.

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