Mutant Bacteria Detects Disease By Changing The Color of Your Urine

Scientists are working on a number of ways to better identify diseases early and noninvasively. A new pair of studies out this week in Science Translational Medicine show promising results from the use of bacterial "biosensors" to detect disease. Two separate research teams successfully manipulated E. coli bacteria to serve as indicators for diabetes and liver cancer by changing the color of ill patients' urine.

The first study explored the use of E. coli as a biosensor for diabetes. One sign of diabetes is that it results in unusually high glucose levels in urine. For this study, researchers genetically modified E. coli so that it turned red at those specific glucose levels. In a test with 13 patients, the bacteria indicated problematically high glucose levels just as reliably as conventional urine dipsticks, which are well-established as effective. The researchers hope their findings will translate to the easy detection in urine of other diseases.

One possibility: liver cancer, which was the subject of the second study. The early stages of metastatic liver cancer are notoriously difficult to identify using imaging techniques like MRIs because they often miss small tumors. At first, the researchers modified the E. coli, which they orally administered to mice with liver cancer, to secrete an enzyme that glows in the presence of cancerous cells. But since this proved too difficult to detect, they engineered a second type of bacteria that, triggered by the glowing E. coli, turned the diseased mice's urine red.

The E. coli  took up shop in the cancerous cells but left the healthy tissue alone, which demonstrates that "probiotics can be programmed to safely and selectively deliver synthetic gene circuits to diseased tissue microenvironments," the researchers say.

They've been monitoring the test mice for a year now, and so far the animals have had no negative side effects from the genetically modified bacteria.