A Synchronous Clock Made of Bacteria

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The activated circuit also produces a protein that breaks down the signaling molecule, providing a time-delayed brake to the cycle. The dynamic interactions of different parts of the circuit in individual and neighboring cells create regular pulses of the signaling molecule and the fluorescent protein, appearing as a wave of synchronous activity. It's "a feat analogous to engineering all the world's traffic lights to blink in unison," wrote Martin Fussenegger, a bioengineer at the Swiss Federal Institute of Technology, in Zurich, in a commentary accompanying the paper in Nature.

The colonies of bacteria are grown in a custom-designed microfluidics chip, a device that allows scientists to precisely control the conditions the microorganisms are exposed to. Changing the rate at which nutrients flow into the chip alters the period of the oscillations, says Hasty.

"The ability to synchronize activity among cells in a population could be an important building block for many applications, from biomedicine to bioenergy," says Ron Weiss, a former TR35 winner and a bioengineer at MIT who was not involved in the research. For example, the bacteria could be engineered to detect a specific toxin, with the frequency of the fluorescence indicating its concentration in the environment. While a microscope is currently needed to read the output, Hasty's team is now working on a version that can be seen with the naked eye.

The oscillator could also be used to deliver drugs, such as insulin, that function best when dosed at certain intervals. "In the future you could think of implants that produce a therapeutic effect," says Fussenegger. The dosing of the drug would relate to the strength or amplitude of the oscillation, while the timing of the dosing would be determined by its frequency. "There would be nothing to worry about for the patient," he says.

Researchers are now trying to make the system more robust, as well as to extend the timescale over which it can synchronize activity. They also want to combine it with previous genetic oscillators, and transfer it into different cell types that might be suited to different biotech applications.