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Bacteria are not well known for their intelligence. They grow, adapt, and grow a little more, but we don’t usually catch them remembering things.
Now, researchers at the University of California (UC), San Diego have used light to imprint a ‘memory’ on a bacterial biofilm, and found that microbes surprisingly act similarly to neurons.
“Our work shows for the first time that simple bacteria can encode memory at the level of their cell membrane potential, which is similar to the memory process of neurons in the brain,” UC San Diego molecular biologist told ScienceAlert, Gürol Süel.
“We were surprised to discover that the mechanism by which memory is formed is similar between bacteria and neurons, since these are very distant evolutionary systems.”
When neurons “fire” in our brains, ions flood the small gap between nerve cells, telling the next neuron that a message has been received and causing it to continue transmitting that message.
Ion flooding produces a cell membrane potential, a difference in the electrical charge between the inside and outside of the cell. Almost all living things use this phenomenon to drive mechanisms in the cell membrane and to transmit signals between different areas of the body.
In neurons, this change in cell membrane potential is known to be involved in the process of memory formation; Now, it seems that something similar can happen in biofilms.
“This membrane potential is a fundamental property shared by all living cells, and particularly well studied in neurons,” explained Süel.
“The bacteria that were exposed to light persistently exhibited a different membrane potential compared to those bacteria that were not exposed, therefore it was clear that these bacteria ‘remembered’ having been exposed to light.”
The team observed a simple bacterial species called the herb bacillus (Bacillus subtilis) and gave them a five second blast of blue laser light. They discovered that this light causes a change in membrane potential, with ions constantly leaving the cell and then coming back in. This effect was maintained for several hours after exposure to light.
Because the bacteria had been genetically engineered for fluorescence when the concentration of the membrane indicator potential, thioflavin-T, increased, the research team was able to physically observe the biofilm while pulsing.
“Cells exposed to light go from hyperpolarization to depolarization, relative to the rest of the biofilm,” the researchers write in the article. “This results in amazing visual patterns over time.”
You can see this in this video below.
Although it appears to be a type of memory formation, it is definitely not the same thing that occurs in our brains. We still don’t know why it occurs or if bacteria actually use it in their regular environments.
“We still don’t know why bacteria have this property. Clearly we need to study more deeply what it means for bacteria to be exposed to light and form memories,” explains Süel.
But what it hints at is that the neurons we trust may have some processes that date back to our evolutionary history like bacteria.
“This finding in bacteria provides clues and an opportunity to understand some key features of the brain in a simpler system,” says Süel in a press release.
“If we understand how something as sophisticated as a neuron came about, its ancient roots, we have a better chance of understanding how and why it works in a certain way.”
This is not the first time that researchers have found bacteria that “remember” things.
A few years ago, a different team of researchers discovered that bacteria had a collective memory that increased their stress tolerance when exposed to salt.
The current team of researchers hopes to be able to use their findings for biological calculus and synthetic biology, but that is still a long way off.
In the meantime, treat the bacteria in your body well … you may remember.
The research has been published in Cellular systems.
