RENEE MONTAGNE, HOST:

We're going to hear, now, about scientists reprogramming life. If you think resetting a clock radio is difficult, try bacteria. NPR's Geoff Brumfiel reports on what researchers are trying to achieve.

GEOFF BRUMFIEL, BYLINE: Walk into Drew Endy's lab at Stanford University and you're not going to see much.

DREW ENDY: It's so crazy, right? It's so invisible. It's like this little invisible stuff. It just looks like we're holding, you know, empty pieces of plastic.

BRUMFIEL: Those plastic Petri dishes aren't empty, though. They're home to tiny colonies of E. coli bacteria. Not the kind of E. coli that makes you sick. These are a laboratory strain, and to Endy, they aren't just single-cell organisms. They're something more.

ENDY: So any system that's receiving information, processing information and then using that activity to control what happens next, you could think of as a computing system.

BRUMFIEL: These little E. coli are out in the world. They're sensing their environment. Is there food? Is the temperature all right? They process this data and make simple decisions about what to do next. Most of the time, it's just whether to reproduce. Endy sees potential for them to do so much more. He wants to take control of a cell's genetic machinery.

ENDY: For us, what's become exciting is the idea that we could get inside the cells and, in sort of a bottom-up fashion, implement computing under our control, under human control, within a biological context within the cells.

BRUMFIEL: Endy is talking about more than splicing in a few extra genes, like scientists already do with crops. He wants to make cells that can follow different programs, like a computer can. To do that, he needed to create, out of DNA something all computers have to have, something that physicists invented way back in the 1940s.

(SOUNDBITE OF PROMOTIONAL VIDEO)

UNIDENTIFIED MAN: The impact of the transistor on the electronic industry and on our society is unquestioned.

BRUMFIEL: This old promotional video from Bell Labs goes on to explain that transistors are simple on/off switches. Computers are made of many millions of these switches. And to program a cell, you need biological switches. As Endy reports this week in Science, he managed to make them.

ENDY: We've made this thing called the transcriptor. The transcriptor is the analog in genetics to the transistor in electronics.

BRUMFIEL: His transcriptor switches are pieces of DNA that he can flip on and off, using chemicals called enzymes. Endy put several of these DNA switches inside his bacteria. That gave him a logic circuit he could use to program the cell's behavior. For example, he could tell a cell to change color in the presence of both enzyme A and enzyme B together.

That's a simple program. If enzyme A and enzyme B, then turn green. This kind of if/then logic is at the heart of computing.

TIMOTHY LU: If my first name is Tim and my last name is Lu, then I am this person Tim Lu.

BRUMFIEL: Tim Lu is at the Massachusetts Institute of Technology. He's also building cellular computers.

LU: This idea of using DNA-based computation is starting to accelerate.

BRUMFIEL: He can see lots of ways that these little biological computers could be used. For example, you could program cells that would automatically scan your bowels for chemical signals of cancer.

LU: These cells could light up, and you could easily see whether the cell has computed whether you may have early signs of cancer or not.

BRUMFIEL: With a little more programming, you might even be able to do something about it.

LU: It could produce drugs that treat the condition, that the circuit is meant to detect or they could express, for example, killer proteins that kill off the cells that are cancerous in nature.

BRUMFIEL: So far, only the simplest logic circuits work. And Drew Endy doubts that these DNA computers will ever outperform a Smartphone. But that's not the point.

ENDY: We're building computers that operate in a place that your cell phone isn't going to work.

BRUMFIEL: And Endy bets that getting even a little bit of computing into places where cell phones will never roam can be very valuable. Geoff Brumfiel, NPR News.

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