Highly secret bacteria
American biologists have adapted glowing strains of E. coli to encrypt and transmit information. With the help of these bacteria, they encoded messages that "hide" from view until a certain time and self-destruct after reading, or require certain reagents to "develop". Article by Palacios et al. InfoBiology by printed arrays of microorganism colonies for timed and on-demand release of messages is published in the journal PNAS, and its summary is given by Nature News (Bacteria encode secret messages).
David Walt from Tufts University (USA) and his colleagues called their invention "bacterial SPAM" – from the English "steganography using printed microbial matrices" (Steganography by Printed Arrays of Microbes). Unlike cryptography, which hides the meaning of a message, steganography hides the very fact of its existence (the simplest example is a letter with "invisible ink").
The idea of encoding messages using biological objects is not new – for example, in 2010, an article was published in Science in which biologist Craig Venter encoded his own name and several well-known quotes in the genome of synthetic bacteria.
The code used by the authors of the new work was much simpler. They created seven different strains of E. coli, each of which produced its own type of luminous substance.
Seven multicolored strains in a Petri dish under different lighting conditions
The scientists prepared two variants of each strain: the first isolated fluorescent substances immediately after the transfer of bacteria to the nutrient medium, and the second – only after several cycles of division of microorganisms. Such a message with a delay increases the secrecy of encoding: the enemy may simply not guess that something is written here at all.
Then biologists prepared a special "paper" – a rectangular matrix of microscopic wells with a nutrient medium. In each such container, you can put a drop with one strain of bacteria. A pair of similar holes sets 49 different combinations: for example, two yellow holes mean the letter t, and orange and green – d. This is enough to encode all the letters of the Latin alphabet, punctuation marks, numbers and some special characters – for example, @. To test their invention, the authors of the article "printed" the first encoded message from "long-playing" bacteria: "this is a bioencoded message from the walt lab @ tufts university 2011" (this is a biocoded message from walt Laboratories at Tufts University 2011). Walt and his colleagues were able to read their opus only two days after applying the "ink" – during this time, the bacteria multiplied and released a sufficient amount of fluorescent substances.
The waiting time can be reduced to eight hours if a second, "fast" type of bacteria is used and a solution of the accelerator substance IPTG (Isopropyl beta-D-1-thiogalactopyranoside) is applied to the sheet with the message, which will force the bacteria to synthesize fluorescent proteins more actively.
Bacterial steganogram after IPTG treatment, taken using equipment from two different companies
(pictures from an article in PNAS)
Biologists note that the complexity of the "cipher" can be increased if a marking gene is inserted into the genome of a bacterium, with which it is possible to distinguish significant microorganisms-letters from background "bacterial noise". To demonstrate the work of this idea, the authors of the article inserted resistance genes to two antibiotics – kanamycin and ampicillin – into two sets of "colored" bacteria.
Scientists have printed two different messages on the same nutritious "paper" with the help of "burglar-resistant" microorganisms. Such a sheet can be treated with one of two medications and read only one of the two messages. Thus, if the reader does not have the correct antibiotic cipher, he will never know what the bacteria are hiding.
In addition, scientists are developing another series of E. coli strains that can be used to print special messages that self-destruct after reading. These bacteria will produce fluorescent substances that change their color after a while. Each letter is encoded by a combination of two bacteria, and if one of them changes its "sign", the message will be hopelessly corrupted.
Experts in the field of steganography note that the work of scientists turned out to be interesting, but very far from practical application. In particular, such messages, in their opinion, can be easily hacked, and they themselves are too fragile.
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of RIA Novosti and <url>
27.09.2011