To record these 'memories', the bacteria use membrane potential, which also plays an important role in the formation of memory traces in people, says Dr. Maja Białecka-Fornal, a member of the research team from the University of California in San Diego (USA).

Until now, only complex, multicellular organisms were believed to possess the ability to remember.

Dr. Białecka-Fornal said: “In our latest work we have shown that seemingly simple organisms, such as bacteria, can 'remember' events from the past, a feature until now attributed to neurons.

“Brief exposure of bacteria to blue light caused them to react differently to external perturbations (medium changes) than bacteria that did not receive the stimulus. In addition, this effect lasted for several hours.”

This means that not only does the bacteria store information about past events somewhere, in addition the process of 'memorizing' occurs at their level of membrane potential (the difference in charge between the two sides of the cell membrane), which also plays an important role in the formation of memory traces in the brain.

Dr. Białecka-Fornal said: “In our research, we have shown that cells exposed to blue light have different ion channel activity (specifically potassium channels). It is similar in the case of neurons, whose activity is related to the flow of charges through ion channels.” 

The scientific team led by Professor Gürol Süel decided to study 'memory' in bacteria after they discovered that these organisms were able to communicate in biofilms (consortia of bacterial microorganisms) using ion channels. Researchers had previously suspected that the way bacteria react depended on the state they had been in before, 'just like neuron activity in the past may affect neuron activity in the future', Dr. Białecka-Fornal says.

“We wanted to see if organisms evolutionarily as distant as bacteria and neurons can use similar mechanisms to record events from the past. And we did it!”

Using a biofilm formed by Bacillus subtilis bacteria, the scientists observed that under the influence of blue light, the membrane potential of bacteria changed and this effect lasted for several hours, even after the stimulus had ceased. Cells exposed to the stimulus reacted differently than their neighbours.

Dr. Białecka-Fornal said: “This means that we are able to directly observe cells that 'remember' perturbations from the past and compare their reactions with neighbours from the same biofilm who have not received the stimulus. In other words, we see memory.”

It is now hoped that the findings can help scientists study the roots of memory as well as understand the formation of neurons.

Białecka-Fornal adds that the discovery could also be the first step towards creating biocomputers - computer systems based on living organisms.

Although the results have opened up many research opportunities, in the near future scientists want to focus on exploring the mechanisms of 'memory' in bacteria and the role it can play in their functioning.

Dr. Białecka-Fornal said: “We need to thoroughly understand the role of "memory" in bacteria and how they can use it. Another question is whether this phenomenon is used in biofilms outside of laboratory conditions.”

Read about the study at: https://doi.org/10.1016/j.cels.2020.04.002.

PAP - Science in Poland, Aleksandra Piasta

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