Researchers harness bacteria for living 'neon' signs

Who would have thought Escherichia coli (E. coli), the bacteria associated with food poisoning, would have quite a big potential benefit  —as living neon signs?

 

Biologists and bioengineers at the University of California in San Diego have created a living neon sign with bacterial "biopixels."

 

"Their achievement, detailed in (a December advance) online issue of the journal Nature, involved attaching a fluorescent protein to the biological clocks of the bacteria, synchronizing the clocks of the thousands of bacteria within a colony, then synchronizing thousands of the blinking bacterial colonies to glow on and off in unison," the university said in a news release.

 

Other potential applications include engineering the bacteria to act as a sensor that can detect low levels of arsenic poison.

 

“Many bacteria species are known to communicate by a mechanism known as quorum sensing, that is, relaying between them small molecules to trigger and coordinate various behaviors. Other bacteria are known to disrupt this communication mechanism by degrading these relay molecules,” said Jeff Hasty, a professor of biology and bioengineering at UC San Diego who headed the research team in the university’s Division of Biological Sciences and BioCircuits Institute.

 

With the biological sensor, decreases in the frequency of the oscillations of the cells’ blinking pattern may indicate the presence and amount of arsenic.

 

Scientists are also looking at using the bacteria's sensitivity to environmental pollutants and organisms to make low-cost bacterial biosensors.

 

The university said one advantage the biosensors have over chemical sensors is that they can respond to changes in the presence or amount of the toxins over time.

 

“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,” said Hasty.

 

He added that since 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.”

 

James Anderson, who oversees synthetic biology grants at the National Institutes of Health’s National Institute of General Medical Sciences, which partially funded the research, said this development shows how basic, quantitative knowledge of cellular circuitry can be applied to the new discipline of synthetic biology.

 

“By laying the foundation for the development of new devices for detecting harmful substances or pathogens, Dr. Hasty’s new sensor points the way toward translation of synthetic biology research into technology for improving human health,” he said.

 

Preceding research

 

The techniques to make the sensor and the flashing display stemmed from the work of scientists in the Division of Biological Sciences and School of Engineering, which they published in two previous Nature papers over the past four years.

 

In the first paper, the scientists developed a way to construct a robust and tunable biological clock to produce flashing, glowing bacteria.

 

In the second paper published in 2010, the researchers showed how they designed and constructed a network, based on a communication mechanism employed by bacteria, that let them synchronize all of the biological clocks within a bacterial colony so that thousands of bacteria would blink on and off in unison.

 

“Many bacteria species are known to communicate by a mechanism known as quorum sensing, that is, relaying between them small molecules to trigger and coordinate various behaviors. Other bacteria are known to disrupt this communication mechanism by degrading these relay molecules,” said Hasty.

 

But while the researchers learned this method could not be used to instantaneously synchronize millions of bacteria from thousands of colonies, they discovered each of the colonies emit gases that, when shared among the thousands of other colonies within a specially designed microfluidic chip, can synchronize all of the millions of bacteria in the chip.

 

“The colonies are synchronized via the gas signal, but the cells are synchronized via quorum sensing. The coupling is synergistic in the sense that the large, yet local, quorum communication is necessary to generate a large enough signal to drive the coupling via gas exchange,” said Hasty.

 

Graduate students Arthur Prindle, Phillip Samayoa and Ivan Razinkov designed the microfluidic chips, the largest of which contain 50 to 60 million bacterial cells and are about the size of a paper clip or a microscope cover slip.

 

Other UC San Diego scientists involved in the discovery were Tal Danino and Lev Tsimring.

 

The smaller microfluidic chips, which contain about 2.5 million cells, are about a tenth of the size of the larger chips.

 

'Biopixels'

 

Each of the blinking bacterial colonies comprise a “biopixel.” Larger microfluidic chips contain about 13,000 biopixels, while the smaller chips contain about 500 pixels.

 

Handheld sensor 

 

Hasty believes a small hand-held sensor could be developed within five years that would take readings of the oscillations from the bacteria on disposable microfluidic chips.

 

This can determine the presence and concentrations of various toxic substances and disease-causing organisms in the field. — TJD, GMA News