Bacterial spam mail

History dictates that Alexander Fleming will be best remembered for his discovery of penicillin, what with him winning the Nobel Prize and all. Perhaps what he should be remembered for, however, are the paintings he made on agar using different coloured bacteria. Quite why this culturally important art form never caught on is anybody’s guess.

It may have been Fleming’s strange hobby that inspired a group of scientists to go one stage further and develop an encrypted messaging system (obviously), which uses printed patterns, known as arrays, of different coloured bacteria. These bugs are coloured by the expression of genetically engineered fluorescent proteins, and the scientists in question have called the system ‘steganography by printed arrays of microbes’, or (ahem) SPAM for short…

Once I got past my initial scepticism and read the paper, I realised this is actually pretty cool stuff. The researchers use Escherichia coli cells that only produce the coloured proteins following treatment with a chemical called IPTG.

So how does it work? You grow your bacterial strains, each capable of expressing a different fluorescent protein, in liquid media in 96-well plates, then print the bacterial cultures onto agar plates – a bit like doing potato printing. Once the bacteria have grown on the plates, they can be pressed onto velvet (an old microbiology trick) or onto a nitrocellulose membrane and put in the post. All the recipient has to do is add IPTG to the material and wait for the bacteria to express their fluorescent proteins.

Of course, a series of fluorescent dots doesn’t really mean anything on its own, so you’d need some kind of cipher to work out what the pattern actually said. Ingeniously, just knowing the cipher isn’t enough – you need to know the chemical inducer needed to make the bugs glow. Add the right one, and the correct fluorescence shows; add the wrong one, and you could get a completely different set of genes expressed, giving you a very different text. Another great aspect is that the message fades when the inducer runs out – a Mission Impossible-style self-destruct.

The future of covert communication’s bright, the future’s fluorescent orange bacteria.

Matt Hutchings

Palacios MA, Benito-Peña E, Manesse M, Mazzeo AD, Lafratta CN, Whitesides GM, & Walt DR (2011). InfoBiology by printed arrays of microorganism colonies for timed and on-demand release of messages. Proceedings of the National Academy of Sciences of the United States of America, 108 (40), 16510-4 PMID: 21949364

Image Credit: kat m research on Flickr

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