Bacteria as Sensors

Imagine going to the doctor's office and a simple administration of a microbe could detect whether you had a life threatening disease in its earliest stages. This is using bacteria as biological sensors.

For years, they've been used to detect pollution in our rivers, lakes, pools and drinking water. Now they can be used to diagnose medical conditions such as tumors in our colons. In a new study, scientists have modified the gut bacterium, E. coli, to be a living sensor for diseases as diverse as diabetes and liver cancer.

For example, in one application, E.coli was designed to leave the gut of a mouse, travel to its liver and 'find' tumor cells. Once in the liver, the E. coli attach to tumor cells. That triggers it to secrete proteins called enzymes that make their way into the urine.

The presence of this enzyme is then detected in the urine when it reacts with a chemical that produces a distinct color reaction. In the experiment, tumor cells were detected in the mouse within 24 hours of deploying the bacterial sensor. This is especially valuable since liver cancer is usually not detected until it's advanced and spread.

Already we have a modified E. coli that reliably diagnoses diabetes by detecting sugar in the urine. It produces a vibrant fluorescent red color making the test easy and sensitive.

So far the experiments have not extended to human trials. We don't know whether allowing bacteria to travel to other organs is risky so a lot more work is necessary. This approach is called a platform technology since its applications can be many, varied, and quite promising.