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Original title: "They don't even have brains, but they have" memories "and can pass them on to future generations?"

wrote an article| Ziv

revisers| Shen mengxi

In our impression, microorganisms are simple organisms with a single mode of activity. Their daily routine is to eat, reproduce, and then die. But biologists have discovered that this simple creature has a powerful memory.

(Image source: giphy) Unlike human memory, microbes apparently cannot remember pi or recite 300 Tang poems. But they can remember what has happened before, where they have been, and even respond to possible future events based on past experiences.

Some scientists use the term "History Dependent Behavior"(HDB) to define the mechanisms by which microbes respond to past experiences. A microorganism that turns grapes into wine is the best example of history-dependent behavior.

Yeast is a key single-celled microorganism in the winemaking process, converting sugars into ethanol and carbon dioxide through anaerobic reactions. We often find grape skins covered with a thin layer of hoarfrost, which contains wild yeasts.

Traditional brewers may prefer to brew with these wild yeasts, or some may choose more controlled, artificially cultivated yeasts, such as Saccharomyces cerevisiae.

Adenosine triphosphate (ATP) stores and transmits energy. There are two ways for yeast to obtain ATP: one is to produce energy by phosphorylation of substrates in the absence of oxygen. In this case, 1 molecule of glucose can produce 2 molecules of ethanol and 2 molecules of ATP.

The second is oxidative phosphorylation in the presence of oxygen, when 1 molecule of glucose can produce 32 molecules of ATP, the efficiency is very high, so usually at this time ethanol fermentation will be inhibited, cell growth has been improved, this phenomenon is called Pasteur effect.

However, glucose is the preferred carbon source for Saccharomyces cerevisiae metabolism, and its presence inhibits gene expression for yeast metabolism of other carbon sources, such as maltose or galactose; in addition, in high glucose concentrations, ethanol and ATP produced in large quantities by glycolysis inhibit respiratory chain activity.

(Image credit: giphy) This explains why yeast cells are able to metabolize glucose in the presence of oxygen in high glucose concentrations. This is called the anti-Pasteur effect, and because it was first discovered by British biochemist H. G. Crabtree, it can also be called the "Crabtree effect."

If glucose is switched to an alternative carbon source that is not preferred, yeast takes a while to turn on the genes that metabolize the alternative carbon source, so there is a long lag time.

However, when cells exposed to this carbon source, even daughter cells within a few generations, switch carbon sources again, their lag time will be significantly shortened, and the researchers believe that some key proteins are at work. These proteins can be preserved and passed on to the next generation.

This in itself is evidence of yeast's historically dependent behavior, but scientists have discovered something more interesting.

If yeast wants to metabolize alternative carbon sources, it must first grow in these carbon sources and therefore need respiration to support it. Scientists found that genes involved in respiration and mitochondrial function played a crucial role in yeast's history-dependent behavior.

(Image credit: giphy) In the process of converting glucose to alternative carbon sources, the "Crabtree effect" mentioned above is suppressed, and genes in respiratory pathways are preferentially induced, and these genes are activated earlier than genes that metabolize other carbon sources.

It was also found that the stronger the respiration of the cells, the shorter the lag time required to switch carbon sources. Bacteria that have undergone carbon source switching can grow more efficiently through respiration and shorten the lag period.

Does this feel familiar? It's similar to vaccination against influenza. After exposure to the pathogen, antibodies are formed in the body, and they can react quickly the next time they encounter this kind of situation.

Yes, vertebrate adaptive immune systems are another form of cellular "memory," and microbial "history-dependent behavior" is similar to this response.

(Image credit: giphy) but the ability of microbes to "remember" could also get us into trouble.

Antibiotics are very effective in treating some bacterial diseases. But bacteria can mutate to produce resistance genes and escape antibiotics, and "superbugs" appear.

One of the mechanisms by which bacteria develop resistance is the formation of biofilms that reduce the effects of antibiotics. One study found that bacteria can remember where they've been and are therefore more likely to form bacterial colonies.

(Image credit: giphy) Scientists have also found that bacteria in biofilms can remember light stimuli they have been exposed to and can retain changes in membrane potential. They think it's a bit like how neurons transmit information.

(Image source: Reference [7]) Some scholars speculate that if bacteria can be reversed to "forget" past behavior patterns and prevent bacterial surface adhesion in the early stage, they can interrupt the formation of biofilm and prevent bacterial infection.

Sometimes it's better to forget...

References:

[1]https://www.frontiersin.org/articles/10.3389/fmicb.2022.1004488/full? utm_source=fweb&utm_medium=nblog&utm_campaign=ba-sci-fmicb-microbe-memory-epigenetics

[2]https://zh.wikipedia.org/wiki/%E4%B8%89%E7%A3%B7%E9%85%B8%E8%85%BA%E8%8B%B7

[3]https://zh.wikipedia.org/zh-sg/%E7%99%BC%E9%85%B5_(%E8%91%A1%E8%90%84%E9%85%92

[4]https://www.zgbk.com/ecph/words? SiteID=1&ID=242730&SubID=153362

[5]http://tech.sina.com.cn/d/i/2018-04-17/doc-ifzfkmth4991548.shtml

[6]https://www.pnas.org/doi/epdf/10.1073/pnas.1720071115

[7] Yang C Y, Bialecka-Fornal M, Weatherwax C, et al. Encoding membrane-potential-based memory within a microbial community[J]. Cell systems, 2020, 10(5): 417-423. e3.

This article comes from Weixin Official Accounts: Bring Science Home (ID: steamforkids), Author: Everything

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