Bacteria in a pill may one day track your body’s chemistry

In the latest twist on an edible sensor that could one day monitor disease, scientists have created a pill-size device that can detect bleeding deep inside a pig’s digestive tract—and relay that information via a wireless signal to a cellphone. If researchers can modify the sensor to pick up other chemicals—and shrink the pill—they could one day create a multipurpose readout of gut health.

To make their sensor, engineers and biologists turned to a bacterium commonly sold as a probiotic in Europe. They genetically engineered it to detect the blood chemical heme by injecting several genes: one that triggers in the presence of heme, and another that makes the cell glow when triggered—enough to light up a detector and produce a wireless signal.

They packaged the 44 million bacteria—along with a battery, light detector, and other electronics—into 10-millimeter-by-30-millimeter pills, which they fed to three pigs. Only pigs with blood in their guts triggered the sensor, the researchers report today in Science .

Other devices have already been created to detect gases in the gut and remotely control sensors using magnets. By picking up on the body’s chemicals and containing several versions of the bacterium, a “super” sensor could one day provide information about cancer, ulcers, or other conditions, the researchers note. Such a supersensor could be a long time coming, other researchers say. For now, the team is trying to shrink this pill by two-thirds by reducing the power demands and the battery size.