Science

Genetically modified bacteria play tic-tac-toe with scientists

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Bacteria are playing tag, it’s unlikely. However, scientists have made this possible by modifying Escherichia coli bacteria. So they were “tuned” to behave like electronic components and act like a neural network, a form of artificial intelligence capable of learning.

“We propose an evolutionary strategy for developing genetic circuits capable of autonomously learning to make decisions under complex conditions,” the researchers summarize in one sentence in their pre-published bioRxiv research report. For now, the “decision making” in question is to make the right choice in a game of tic-tac-toe: which box? Not so strange, since this test is often used to test artificial intelligence systems.

It all started in 2019 with the work of another research group. A strain of a particular bacterium, Escherichia Coli, has been genetically engineered to sense 12 different chemicals and respond appropriately by changing the activity of certain genes. This variety was nicknamed “Puppet”.

The research team took this work and applied other modifications. They combined many copies of two circular pieces of DNA called “plasmids”. Each of these plasmids “encodes” a separate fluorescent protein. One is red, the other is green. The ratio of these two plasmids present in bacteria, and therefore their final color, is not predetermined: it is also affected by 12 different chemicals, as well as some antibiotics. If no such modification is applied, the ratio remains constant. Thus, the composition of DNA forms a kind of “memory”, frozen until the next modification.

When, conversely, new “data” is introduced with the help of chemicals or antibiotics, the ratio (and therefore the color) changes, but with respect to the previous configuration. This means that some memory is retained and hence some form of learning is possible. This behavior is similar to that of an electronic component called a “memristor”. Therefore, scientists called this new biological “component” “memregulons.”

Biological memristors

A memristor is essentially a component similar to a transistor that can not only process but also store data in its internal memory. This is a component that is used, in particular, to create so-called “neural networks”. Indeed, today, in many cases, what is called “artificial intelligence” consists of a system that is “filled” with a large amount of data to “learn” and extract logical connections to achieve a given goal. Recognize faces, texts… OR play tic-tac-toe… These learning methods are based on the functioning of biological neurons. Today they are closer to statistical methods. Therefore, we are talking about “artificial neural network”. The data sent circulates in an artificial “grid” of neurons, usually virtual ones. In fact, these are points in the network, “connected” to each other by computer code. Thus, this network receives incoming information, training data and transmits outgoing information.

From the moment bacteria can take in input (chemical or antibiotic), transmit the “result” (DNA modification and therefore color), while keeping the previous data in memory, one can understand the comparison that is being made. Similarly, scientists set out to create a “neural network” with these bacteria.

The result was a system that could adapt, learning from its past behavior, reprogramming itself—in short, like a learning AI. In the cancer lice example, the scientists did the following: a bit like “training” bacteria, they applied “reinforcement” learning, that is, with a system of reward and punishment depending on whether the action was performed. strategic enough or not.

These bacteria were cultured in compartments corresponding to the crab mesh. Each time a person plays, the bacterium is “informed” by adding a chemical product to a compartment, with each product corresponding to a specific location. If at first the bacterium “played” its next move randomly, it eventually learned through reinforcement by being “punished” by adding antibiotics when the play action was bad. However, not everything is so simple: the game took several days.

The demonstration concerns a crab, which is fairly harmless. However, according to scientists, the possibilities of their research are very extensive. “Changed gene circuits could give living cells the ability to make decisions,” they say. They might become able to “reprogram” themselves into much more complex decision-making contexts.

Source bioRxiv

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