Bacterial Circuits

By interfacing bacteria to silicon chips, researchers have created a device that can sense almost anything.

Like a canary in a mine, a microbe can often sense environmental dangers before a human can. It's easy to see a canary's reaction. But how can you can you tell what a microbe's feeling? How can you coax a microbe to communicate?

One way is to interface it to a silicon chip.

University of Tennessee microbiologist Gary Sayler and his colleagues have developed a device that uses chips to collect signals from specially altered bacteria. The researchers have already used these devices, known as BBICs, or Bioluminescent Bioreporter Integrated Circuits, to track pollution on earth. Now, with the support of NASA's Office of Biological and Physical Research, they're designing a version for spaceships.

Sayler's group, which includes Tennessee researchers Steve Ripp, Syed Islam and Ben Blalock, as well as collaborators at JPL and the Kennedy Space Center, has bio engineered microbes that glow blue-green in the presence of contaminants. Then they joined those bacteria to microluminometers - chips designed to measure the light.

more Glowing colonies of microbes

What BBICs offer, explains Sayler, is a low-cost, low-energy way to detect pollutants. They're tiny: each BBIC is about 2 mm by 2 mm, and the entire device, including its power source, will probably be about the size of a matchbox, and they monitor their surroundings continuously.

NASA is interested in sensing contaminants because spaceships are tightly sealed. Unseen fumes from scientific experiments or toxins produced by molds and other biofilms can accumulate and pose a hazard to astronauts. BBICs can be crafted to sense almost anything: ammonia, cadmium, chromate, cobalt, copper, proteins, lead, mercury, PCBs, ultrasound, ultraviolet radiation, zinc - the list goes on and on.

The system is surprisingly rugged. Microbes thrive in a wide range of environments, so it's possible to design BBICs that can survive in extreme or highly contaminated surroundings. "They can actually do their job sitting in things such as jet fuel-water mixtures," marvels Sayler.

Although the microbes can protect themselves from toxins, they still have a variety of needs - food, for example. Keeping them alive, Sayler says, "is a significant portion of the work."

One problem is that microbes must be immobilized so that they remain right next to the chip. The challenge, says Sayler, is trying to figure out how to immobilize the microbes in such a way that they survive as long as possible.