Message in a Bacterium May Be Next “Invisible Ink,” Study Says

By Elizabeth Lopatto – Sep 26, 2011 8:00 PM GMT+0100

Scientists encrypted a secret message into genetically-engineered E. coli bacteria using a method that one day may be useful for preventing counterfeiting or covert communications.

The E. coli were modified to glow and express one of seven colors, which were used to create a coding system that allowed for the entire alphabet, the digits 1-9 and some symbols, according to a paper in the journal Proceedings of the National Academy of Sciences.

E. coli, better known as a source of food poisoning, when encoded can be used like “invisible ink,” containing messages that can’t be detected until the recipient unlocks the secret message imprinted on paper with a special bacteria-growing solution. The method may be more effective than transmitting sensitive data electronically, researchers said.

“It’s another layer of protection, a way of sending secure messages, preventing counterfeiting and providing authentication,” said David Walt, the study’s head author and a chemist at Tufts University in Medford, Massachusetts. “We haven’t thought out all the different applications yet. We could put a time-encoded message so things develop at different times, so you could have one message initially and then another. Or you could have a self-destructing message like in ‘Mission Impossible.’”

The research was funded by the U.S. Department of Defense through its Defense Advanced Research Projects Agency.
Bacterial Broth and Paper

E. coli messages are grown in bacterial broth, and then copied onto a white, paper-like membrane. The membrane containing the undeveloped message is then sent to a receiver, who can stamp it onto a growth plate to develop the bacteria and then translate the color coding back into language. In the experiment, the deciphered message read, “this is a bioencoded message from the Walt lab at Tufts university 2011.”

Frequently targeted by hackers, companies and governments find it increasingly difficult to keep electronic data private from those who might “eavesdrop” on its transmission, Walt said. In very sensitive circumstances, such as espionage, encrypting information using microbes may prevent such attacks, he said.

For added security, the sender and receiver agree on growth conditions — certain chemicals in the growth medium. If the message is intercepted and grown without the right chemicals, the message will read as gibberish, or as a different message, the paper showed.

The simplest way to encode a message without using sophisticated instruments was to use color, he said. Future research may focus on using time-encoded messages, where it takes days or months for the message to be grown in the bacteria, Walt said.

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