Spies could hide messages in gene-modified microbes

"Forget invisible ink or lemon juice – spies can now send messages hidden in genetically engineered bacteria. The new method, dubbed steganography by printed arrays of microbes (SPAM), uses a collection of Escherichia coli strains modified with fluorescent proteins that glow in a range of seven colours.

Each character of the message is encoded using two colours, creating 49 possible combinations – enough for the alphabet, the figures 0 to 9 and a few other symbols. "You can think of all sorts of secret spy applications," says David Walt, a chemist at Tufts University in Medford, Massachusetts, who led the research.

Messages are grown on agar plates then transferred to a thin film that can be sent in the post to the recipient. The film appears blank in everyday conditions, but the message is revealed when the recipient transfers the bacteria to an appropriate growth medium.

As well as giving the bacteria their fluorescent palette, genetic modification also defines which growth medium they will respond to – so the medium type can act as a secret key. For example, bacteria engineered with resistance to a certain antibiotic will display a message only when treated with that particular chemical – any other antibiotic will produce gibberish, or could even display a message warning that the wrong key has been used. Walt says that combining a number of genetic traits could lead to thousands of possible keys.

It is also possible to develop bacteria that lose their fluorescent properties over time, creating a message that self-destructs in the style of Mission Impossible."


via New Scientist/read more