Justin Gallivan, PhD, assistant professor of chemistry, and graduate student Shana Topp successfully reprogrammed E. coli's chemo-navigational system to detect, follow and precisely localize to specific chemical signals. In doing so, the scientists exploited E. coli's natural chemotaxis, a microbe's ability to move toward specific chemicals in its environment.

"Equipping bacteria with a way to degrade pollutants, synthesize and release therapeutics, or transport chemicals with an ability to localize to a specific chemical signal would open new frontiers in environmental cleanup, drug delivery and synthetic biology," says Dr. Gallivan.

The researchers equipped E. coli with a "riboswitch," a segment of RNA that changes shape when bound to certain small target molecules, which can then turn genes on or off. Dr. Gallivan and Topp believe that the riboswitch can be used to equip other types of self-propelled bacteria with "chemo-navigation" systems to move them toward desired targets.

Chemotactic bacteria navigate chemical environments by coupling their information-processing capabilities to powerful, tiny molecular motors that propel the cells forward.

Researchers have long envisioned reprogramming bacteria so that microbes capable of synthesizing an anti-cancer drug, for instance, can be used to target diseased cells while sparing healthy cells of side effects. Likewise, scientists are researching ways to use bacteria to clean up oil spills or remove other pollutants from soil, water and wastewater.

"This new ability to equip motile bacteria with a precise and tunable chemo-navigation system will greatly enhance the impressive arsenal of natural and engineered cell behaviors," says Dr. Gallivan.

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