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In the first discovery, scientists confirmed that bacteria have a 24-hour body clock



In the first discovery of its kind, scientists discovered that a non-photosynthetic bacteria is regulated by the circadian rhythm closely related to many other life forms.

In humans, our circadian rhythm is like the biological clock in cells, which controls almost all processes in our body, affecting our sleep and wake-up time, as well as the function of metabolism and cognitive processes.

This internal timekeeping takes about 24 hours to run, which is driven by our biological clock, and the same core phenomena have been observed in many other kinds of organisms, including animals, plants and fungi.

However, for a long time, it has not been clear whether the entire bacteria is also governed by the circadian rhythm.

This phenomenon has been proved in photosynthetic bacteria, which use light to produce chemical energy, but whether other types of bacteria also have a circadian rhythm is still a mystery.

Martha Merrow, a time biologist at Ludwig Maximilian University in Munich, explained: “For the first time, we have discovered that non-photosynthetic bacteria can tell the time.”

“They adapt molecular work to the time of day by reading the cycle of light or temperature.”

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In a new study, Merrow and other researchers Bacillus subtilisIt is a rigorously researched strong bacteria found in the soil and gastrointestinal tract of many animals (including humans).

and Bacillus subtilis It is not photosynthetic, it is sensitive to light due to photoreceptors, and previous observations of microorganisms have provided clues indicating that its gene activity and biofilm formation process may follow a cycle daily in response to environmental cues, which may be based on Changes in light level or temperature.

To conduct the study, the researchers measured the gene expression activity of bacteria in cultures exposed to constant darkness or alternating light for 12 hours and then darkness for 12 hours a day.

In the alternating light-dark cycle, the expression of a gene called ytvA, which encodes a blue light photoreceptor, increases during the dark phase and decreases during the light phase, indicating that the biological clock is entrained in the circadian rhythm.

When in constant darkness, the cycle still exists Bacillus subtilisAlthough the cycle is extended, it does not strictly follow the 24-hour cycle, and there is no light signal to turn off.

In another experiment, the researchers conducted a temperature cycling experiment, which is another method of stimulating diurnal heat changes.

Again, with the temperature cycle between 12 hours at 25.5°C (77.9°F) and 12 hours at 28.5°C (83.3°F), the expression of ytvA weakens and flows, and the cycle continues like light Free-run experiments (not synchronized with environmental prompts), although the cycle is longer.

Combining all the results, the researchers concluded Bacillus subtilis There is a circadian clock, expressed as a free-running circadian rhythm and a systematic entrainment of environmental cues (ie, the Zeitgeber cycle).

Although the current discovery involves only one type of bacteria, this is the first time this phenomenon has been found in any non-photosynthetic bacteria, which may have a huge impact on our understanding of bacteria as a whole: about 15% of the total number of bacteria on earth Creatures.

Anthony Dodd, a circadian researcher from the John Inness Center in the United Kingdom, said: “Our research opens the door to the study of circadian rhythms across bacteria.”

“Now we have determined that non-photosynthetic bacteria can tell us that it takes time to find out the processes in the bacteria that cause these rhythms and understand why the rhythms provide advantages for the bacteria.”

Currently, the research team speculates that the circadian rhythm may be regulated by a transcription-translation feedback system in some way, or may be related to the metabolic cycle.

It is also unknown whether a form of the overall “master clock” can be controlled Bacillus subtilisAs humans have suggested, our circadian rhythm remains the same, although the research team points out that it is possible.

“It would be helpful to investigate whether temperature and light are inputs to a master pacemaker, or whether they are useful information Bacillus subtilis There may be multiple oscillators, as described for various single-cell and multi-cell organisms. “The author wrote in the paper.

“It’s possible Bacillus subtilis There may be a main oscillator or one or more downstream oscillators coupled to and driven by the main pacemaker. “

In any case, the consequences of the bacterial 24-hour biological clock may have huge consequences-not only the scientific understanding of bacterial biology, but also its potential use in biomedicine, agriculture, industry and other fields.

Bacillus subtilis From washing powder production to crop protection, its application range is wide. [and] Probiotics for humans and animals. Said Ákos Kovács, a bioengineer at the Technical University of Denmark.

“So building a biological clock in this kind of bacteria will reach its culmination in various biotechnological fields.”

The findings are reported in Scientific progress.


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