By DRS. DAVID NIESEL AND NORBERT HERZOG

For all the harm they can do, bacteria also benefit people in many ways. Bacteria are part of many foods we enjoy, harnessed to produce medicines such as insulin, indispensable in manufacturing chemicals and used to detect pollution in the environment. Now they are now being used as living biological sensors.

In the emerging field of synthetic biology, new roles for these single-celled organisms are being developed. Scientists from the Massachusetts Institute of Technology, the University of California San Diego, Stanford and a research team in France have modified the gut bacterium E. coli to be a living sensor for a variety of diseases such as liver cancer and diabetes. The scientists have bioengineered the E. coli bacterium so that it reacts to specific changes that occur in the body with disease. This causes the E. coli to change or acquire new properties or characteristics that are easily detectable.
In one example, E.coli was engineered to leave the gut and find tumor cells in the liver of a mouse. Once E. coli attaches to tumor cells in the liver, they produce specific enzymes which make their way into the urine. The presence of this enzyme can be detected easily because it reacts with a chemical causing it to change color. This means that when tumor cells are present in the mouse’s liver, the enzyme in mouse’s urine will be detected by the color change.
 

This detection method is quick, easy, noninvasive and it could save lives. Currently, it is difficult to detect tumor cells in the liver during the early stages of cancer, so people are not typically diagnosed with liver cancer until the tumor has spread to other organs. This makes it difficult to treat and leads to high mortality rates. Early detection will allow for a range of treatment options which are likely to extend or save people’s lives. In the future, scientists plan to further engineer the tumor-seeking E. coli to deliver chemotherapeutic drugs directly to the cancer cells.

Another bioengineered E. coli has been developed to reliably identify diabetes by detecting elevated glucose in the urine. This E. coli produces a vibrant fluorescent red color in response to the sugar in the urine, indicating a diabetic state. This method of detection also has a low false positive rate, meaning the engineered E. coli rarely indicated diabetes was present when it wasn’t.

Currently, the vast majority of these experiments have been limited to mice, and there could be challenges in applying this technology to humans. For example, allowing bacteria to invade from the intestinal track to internal organs could be risky for those with other health issues or weakened immune systems.

However, there appears to be a substantial upside in the use of bacterial sensor technology. Expect to see more examples of synthetic biology and bacterial sensors in the future. You can imagine how this engineered E. coli could be modified to produce diagnostics for other tumors or diseases.

Medical Discovery News is a weekly radio and print broadcast highlighting medical and scientific breakthroughs hosted by professor emeritus Norbert Herzog and professor David Niesel, biomedical scientists at the University of Texas Medical Branch at Galveston. Learn more at www.medicaldiscoverynews.com.