Bacteria used to create living 'neon signs'

Posted by Emma Woollacott

Scientists have created a living 'neon sign' made of millions of bacterial cells fluorescing in unison.

The UC San Diego biologists and bioengineers attached a fluorescent protein to the biological clocks of a bacterial colony, then synchronized them to glow on and off together using the bacteria's own communication mechanism.

The end result is a microfluidic chip that contains 50 to 60 million bacterial cells and is about the size of a paper clip. Each colony comprises what the researchers call a 'biopixel', an individual point of light, with the larger microfluidic chips containing about 13,000 biopixels.

Using the same technique, they also engineered a simple bacterial sensor that can detect low levels of arsenic, with a decrease in the frequency of the cells’ blinking pattern indicating the presence and amount of the poison.

Because bacteria are sensitive to many kinds of environmental pollutants and organisms, the scientists believe that, within five years, similar low cost bacterial biosensors could be used to detect a wide range of heavy metal pollutants and disease-causing organisms.

"These kinds of living sensors are intriguing as they can serve to continuously monitor a given sample over long periods of time, whereas most detection kits are used for a one-time measurement," says biology and bioengineering professor Jeff Hasty.

"Because the bacteria respond in different ways to different concentrations by varying the frequency of their blinking pattern, they can provide a continual update on how dangerous a toxin or pathogen is at any one time."

The biological clocks of the bacteria are synchronized using a mechanism known as quorum sensing, whereby small molecules are relayed between individual bacteria to trigger and coordinate various behaviors. However, this only works for members of the same colony.

"If you have a bunch of cells oscillating, the signal propagation time is too long to instantaneously synchronize 60 million other cells via quorum sensing," says Hasty.

But the team discovered that each of the colonies emits gases that, when shared among the thousands of other colonies within a specially designed microfluidic chip, can synchronize all the millions of bacteria in the chip.

The UC San Diego Technology Transfer Office has filed a patent application for the invention.