Technology The blob, the unicellular organism able to learn ......

The blob, the unicellular organism able to learn … without brain!

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This creeping organism formed of a single giant cell has no brain. Yet he is able to learn from his experiences and pass them on to his fellow creatures.

It is not an animal, nor a plant, nor a mushroom. The "blob", or Physarum polycephalum of its scientific name, is a unicellular creeping being – it is composed of a single cell, against 100 000 billion in the human body – which has been living in the undergrowth for hundreds of millions of years. years. But this year, he makes his entry into a zoo, that of Paris, the Bois de Vincennes, the first in the world to accommodate this species. The latter has taken up residence in the vivarium, where the public will be able to meet him from Saturday. Three years ago, the Express had already looked into this unclassifiable being. Presentations.

Although devoid of mouth, stomach or brain or nervous system, he eats, moves and is even able to learn from his experiences, as demonstrated for the first time by biologists Toulouse III University , in April 2016. In another study, published in the journal Proceedings of the Royal Society Bthese same researchers have determined that the blob is also able to transmit what it has learned by merging, even temporarily, with its congeners.

Cross a salt bridge, feed, teach

In their first experiment, researchers Audrey Dussutour and David Vogel taught the blobs to cross a bridge covered with repellent substances – but harmless – for them, such as coffee, quinine or salt, to reach their food.

Blob learns by habituation to ignore the presence of quinine (a bitter substance) on its way to food. A narrow pseudopod (the outgrowth of the cell used to join the food) is synonymous with a repulsive behavior, a large pseudopod represents a normal behavior.

Blob learns by habituation to ignore the presence of quinine (a bitter substance) on its way to food. A narrow pseudopod (the outgrowth of the cell used to join the food) is synonymous with a repulsive behavior, a large pseudopod represents a normal behavior.

Audrey Dussutour / CNRS

During the second experiment, they wanted to check if the blobs could transmit their learning by merging with their congeners. Because Physarum polycephalum, composed of thousands of nuclei, naturally has the ability to fragment in the presence of obstacles and merge with one or more congeners. "He then forms a new unicellular being," says Audrey Dussutour, interviewed by L'Express, "it is a very particular organism, in a fusion of 1 + 1 = 1 and even 1 + 1 + 1 + 1 = 1."

The two scientists observed more than 4,000 separate blobs in two groups in 2000. All had to cross a bridge to get food. The first, the "experienced", had to learn to go through a salt bridge to feed themselves. The second, the "naive", had to cross a bridge virgin of any repulsive substance.

A blob to control them all

The scientists then formed pairs of "experienced" blobs, pairs of "naive" and mixed "naive-experienced" pairs to merge with each other. Then they again forced these blobs to cross a bridge covered with salt. Surprise: Mixed blobs were faster than naïve blobs, as if learning the harmlessness of salt had been shared. Audrey Dussutour and David Vogel then reproduced the experiment with trios and fused blobs quartets: the result remained the same regardless of the number of merged "naive" blobs: as long as an experienced is part of the equation, the learning is shared.

But that was not enough to prove that a transfer of information had taken place. So the scientists did the same experiment, but this time, they separated (by cutting them in half) the "naive and experienced" blobs that had merged either after one hour or after three. As a result, only naive blobs that had merged for at least three hours with an experienced blob ignored salt, while the others showed strong dislike. The information was thus passed on to naive people only after a merger of at least three hours.

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Two experienced blobs (H) merge with a naive (N) congener. The pseudopodium that crosses the bridge comes from naive blob. At the level of the contact zone (zoom) we can see the formation of a vein between the blobs.

Two experienced blobs (H) merge with a naive (N) congener. The pseudopodium that crosses the bridge comes from naive blob. At the level of the contact zone (zoom) we can see the formation of a vein between the blobs.

David Vogel / CNRS

The researchers then observed the fused blobs under the microscope (see this short video) and noticed that a vein formed between them after … three hours of contact. According to them, it is very likely that this information circulates.

"Our next study will consist in trying to understand the mechanisms at work in the exchange of information, explains Audrey Dussutour, that is to say how they are transmitted: by RNA transcription, by protein exchange? So let's learn four different blobs – one will learn to ignore salt, the other quinine, etc. – and then we'll merge them together to see how and what information is exchanged. "

The purpose will be to determine if there is a conflict between the information or if they are each exchanged – and therefore "coded" – independently. "If we discover that a cell is capable of doing this without a nervous system (without brainit will be really interesting, "says the biologist, which could open up interesting avenues, particularly in medicine." Our work could inspire research on bacteria. Because if they can learn too, maybe they can be deceived too? "

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