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'Neon signs' made with bacteria

Thousands of fluorescent E. coli bacteria make up a biopixel.Hasty Lab / UC San Diego

The bar of the future may have all-organic brews on tap and blinking neon signs in the window made with millions of bacterial cells that periodically glow in unison.

The same "living neon sign" technology could also be used to help brewers and other folks monitor environmental pollutants in water such as arsenic, according to research published online Sunday in the journal Nature.

The breakthrough involved attaching a fluorescent protein to bacteria engineered with biological clocks, and then synchronizing the clocks of thousands of bacteria within a colony to create a so-called biopixel.

Thousands of these biopixels, each an individual point of light like a pixel on a computer screen, are then synchronized so they all glow in unison to create a sign.

The largest signs made so far are about the size of a paperclip, according to the researchers working on the technology at the University of California at San Diego. 

Path to success

The work started with engineering a biological clock into a single bacterium, explained Jeff Hasty, a professor of biology and bioengineering at the university.

These engineered clocks are attached to a fluorescent protein that flashes on and off. 

Next, Hasty's team synchronized all the clocks in a bacterial colony via what's called quorum sensing, which is a way bacteria communicate with each other using molecular signals.

This made it so that "an entire colony would flash in synchrony," Hasty explained to me Monday.

A single bacterial colony is 10s of microns in diameter — about the size of a pixel, hence biopixel.

"If you want to get out to the centimeter-length scale, this quorum sensing won't work because it is too slow; you would get something that looks like waves," he said.

To get over that hurdle, the team connected a gene that codes for hydrogen peroxide gas vapor to the biological clock. The gas vapor is used to communicate and synchronize the colonies.

"When the clock goes on, you get a pulse of vapor and that pulse of vapor then goes to a neighboring colony and that's what communicates the signal. And when the clock goes off, the vapor goes off," Hasty said.

In the final system, quorum sensing is used for signaling at the colony level, the gas vapor signal is used to synchronize across colonies.

Environmental sensors

The researchers have turned the blinking bacteria into a sign that spells out UCSD and could, for example, get to the scale where it could spell your favorite brand of beer for display in a bar window, Hasty said.

More practical applications will come in the environmental sensor market. As a proof of concept, the team created a biosensor that detects levels of arsenic, a heavy metal, in water. The more arsenic detected, the slower the sensor blinks. 

These sensors can be built in the lab for less than $100, Hasty said, and each sensor lasts for weeks at a time.

For now, the researchers are trying to figure out the limits of scale for the technology. 

"How many cells can we get in a centimeter-length scale to increase the signal?" Hasty said. "And then, how much can we increase this length scale to get something that is even macroscopic?"

Imagine, for example, a giant flashing "living neon sign" hovering over the outfield seats advertising the marquee sponsor for the Colorado Rockies baseball team.

More on glowing life forms:

John Roach is a contributing writer for To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.