A neon sign of bacterial cells  (Source: UC San Diego)
The biological sensor shows the presence and levels of arsenic through the frequency of the oscillations of the cells' pattern of blinking

Just in time for the Christmas season are cells that resemble Christmas twinkle lights. University of California - San Diego scientists have created neon signs made of blinking bacterial cells, which could eventually be used to detect toxic substances and their concentrations.

The research, which was led by Jeff Hasty, professor of biology and bioengineering at UC San Diego, involves binding a fluorescent protein to the biological clocks of the bacterial cells, then synchronizing these biological clocks. This leads to the simultaneous blinking of the glowing cells.

The researchers created the neon signs of bacteria by tapping into their natural form of communication amongst each other. Bacterial cells are synchronized via quorum sensing, where they relay molecules between one another to initiate and synchronize certain behaviors. However, using this method to synchronize millions of bacteria from different colonies is challenging.

To remedy this issue, the research team studied a method where colonies of bacteria emit gases which, when shared, can synchronize different colonies rather than just one. By using quorum sensing to kick-start the gas exchange, researchers were able to synchronize colonies of bacterial cells within a special microfluidic chip, which can contain as many as 60 million cells.

Each colony of blinking cells makes up a biopixel, which is similar to a pixel on a computer screen. Larger microfluidic chips can contain as many as 13,000 biopixels.

Here's a video that offers a demonstration of the process in which the "neon signs" were made:

The glowing cells may sound like Lite Brite knock-off, but the project has potential real-world applications. According to Hasty and the research team, these glowing bacterial cells can be used to make living sensors that detect toxic substances such as arsenic. The advantages of a biological sensor over traditional chemical sensors is that the living version can respond to the presence and amount of toxic substances in an area over time due to its living organisms. Bacteria are very sensitive to their environmental surroundings.

In fact, Hasty and his team have already created a living sensor that is capable of detecting low arsenic levels. The biological sensor shows the presence and levels of arsenic through the frequency of the oscillations of the cells' blinking.

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

Hasty sees such handheld sensors for all types of toxic substances becoming a reality within five years.

Source: UC San Diego

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