"Ribocomputer" in E. coli
Scientists have turned E. coli into a universal biocomputer
Geneticists have turned an ordinary E. coli into a biological analogue of a computer, the role of electrical signals in which short RNA molecules play, and created a record-breaking complex logic circuit based on it, according to an article published in the journal Nature (Green et al., Complex cellular logic computing using ribocomputing devices).
"We even managed to embed two logic devices independent of each other into one bacterium that secrete two different types of luminous proteins. This opens the way for the creation of biosensors that fit entirely into one cell. In addition, such a system is easy to transplant into other types of microbes," says Kim Jongmin from Harvard University (in a press release Programming cells with computer–like logic - VM).
Over the past decade, biotechnologists have developed many miniature bio-devices that repeat the functions of their inanimate counterparts. In particular, there are already several dozen DNA computers, a full-fledged computing device and a display from E. coli colonies, and two years ago biologists from the United States created a biocomputer combining several different strains of microbes.
All such "bio-digital technologies" have two common drawbacks – their work cannot actually be changed without completely changing the DNA of microbes, and they work extremely slowly due to the speed at which DNA is read and information is distributed in the world of microbes. For this reason, scientists have created quite a lot of simple biocomputers that perform one logical operation, and very rarely tried to create something more complex.
Johnmyn and his colleagues were able to circumvent this problem by creating the first universal biocomputer capable of performing all the functions of semiconductor processors, replacing DNA strands commonly used in such bacterial "processors" with short RNA molecules similar in shape to pins or hairpins.
These pins, as scientists explain, can change their shape if another RNA molecule with a suitable set of "letters" is attached to them. This is important because the shape of the RNA strand determines whether the ribosome, the cellular protein assembly factory, can read it and assemble a full-fledged protein molecule that forces the cell to change its behavior or send a certain signal.
Accordingly, by combining different types of hairpins and DNA strands connected to them, it is possible to create analogs of logic elements in semiconductor chips capable of performing the same operations, such as AND, OR, excluding OR and NOT.
This is where the second important property of these RNA molecules comes into play – they are completely synthetic and molecules similar to them do not occur inside microbes. This allows you to "glue" virtually any number of such "logical nodes" without fear that their work will be interfered with by processes inside the microbes themselves or neighboring logical chains.
Guided by similar ideas, scientists have created several universal computational blocks of RNA molecules capable of processing all four basic logical operations and checking any logical expressions. After making sure that they work, they combined several such blocks into a complex system of 444 links, performing 12 logical operations and processing five different chemical signals.
Such RNA computers, as scientists note, can in the future be used to observe complex processes inside living cells, as well as to create "live" sensors capable of recognizing various changes in environmental conditions and reporting this to a person.
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28.07.2017