Forget the dog—Teach bacteria new tricks

EMORY (US)—Can we program germs to do our dirty work? An Emory University chemist has moved science another step closer to that possibility by teaching an innocuous strain of E. coli to “seek and destroy.”

“Rather than just altering a single gene and getting a cell to do one task, we can start thinking of a cell almost like a computer that we can reprogram to do a series of things,” says Justin Gallivan, associate professor of biomolecular chemistry at Emory.

Gallivan is working at the forefront of an area known as synthetic biology. A major goal of this field is to reprogram bacteria to carry out complex tasks, such as synthesizing and delivering drugs, and tracking and cleaning up environmental pollutants. Gallivan’s recent efforts have targeted the molecules of an herbicide called atrazine that has been banned in the European Union, but remains one of the most widely used herbicides in the United States, with millions of pounds of it applied annually.

“The bacterium E. coli swims toward things it likes and away from things it doesn’t,” Gallivan says. “It communicates with other cells. It synthesizes complicated compounds and replicates itself every 20 minutes. Put another way, E. coli tastes, thinks, talks, listens, and makes things.”

The program for all of these activities is packed into the genome of the bacterium, and is in part regulated by RNA switches, known as riboswitches. By hacking into the E. coli program and inserting a synthetic riboswitch, Gallivan’s team reprogrammed the E. coli cell’s chemical navigation system.

The presence of atrazine flips the synthetic riboswitch, causing the bacterium to move toward high concentrations of the herbicide. In addition, the researchers incorporated genes from atrazine-eating bacteria into the E. coli, so the bacterium performs a second task—consumption.

“The E. coli essentially use the atrazine molecules as food, breaking them down into something less harmful,” Gallivan explains.

Gallivan focuses on fundamental research at the interface of chemistry, biology and materials science. “My interest is reprogramming simple organisms to get them to do new things, in a rational and predictable way,” he says. “A revolution is going on in biology. We’re really starting to understand the systems of living things at the molecular scale. Instead of asking, ‘What is the nature of this organism?’ We can begin asking, ‘What can we do with this organism?’”

His research is funded by a grant from the National Institutes of Health.

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