In a first discovery of this kind, scientists discovered that a species of non-photosynthetic bacteria is regulated by the same circadian rhythms that are based on so many other life forms.
In humans, our circadian rhythms act as a kind of biological clock in our cells, controlling virtually all processes in our body, influencing when we sleep and get up, plus the functioning of our metabolism and cognitive processes.
This preservation of internal time, which revolves around a 24-hour cycle, is driven by our circadian clock and the same basic phenomenon has been observed in many other types of organisms, including animals, plants, and fungi.
However, for a long time, it was not clear whether bacteria in general are also subject to the dictates of circadian rhythms.
The phenomenon has been demonstrated in photosynthetic bacteria, which use light to produce chemical energy, but whether other types of bacteria also possess circadian clocks has long remained a mystery – until now.
“We discovered for the first time that non-photosynthetic bacteria can tell the moment,” explains chronobiologist Martha Merrow of Ludwig Maximilian University in Munich.
They adapt their molecular functioning to the time of day by reading the cycles in light or in the temperature environment.
In a new study, Merrow and research colleagues examined Bacillus subtilis, a resistant, well-studied bacterium found in the soil and gastrointestinal tract of many animals, including humans.
While B. subtilis is not photosynthetic, is sensitive to light due to photoreceptors, and previous observations of the microbe have indicated that gene activity and biofilm formation processes could follow a daily cycle in response to environmental cues, probably based on light levels or changes in temperature.
To investigate, the researchers measured bacterial gene expression activity in cultures exposed to either constant darkness or an alternate daily cycle of 12 hours of light followed by 12 hours of darkness.
In the alternating light / dark cycle, the expression of a gene called ytvA – which encodes a blue light photoreceptor – increased during the dark phase and decreased during the light phase, indicative of the processes of entrainment in a circadian clock.
When subjected to constant darkness, the cycle still exists in B. subtilis, although the period was extended, not strictly following a 24-hour cycle without the light signal going out.
In another experiment, researchers experimented with temperature cycles, which is another way to stimulate heat changes between day and night.
Again, ytvA expression decreased and decreased as temperatures moved between 12 hours at 25.5 ° C (77.9 ° F) and 12 hours at 28.5 ° C (83.3 ° F). and, as in the case of light, the cycle persisted in a free-running experiment (it is not synchronized with environmental indices), although with a longer period.
Taking all the results together, the researchers conclude B. subtilis has a circadian clock, exposed to circadian rhythms of free running and systematic training to environmental cues known as zeitgeber cycles.
While the findings relate to only one bacterial species at the moment, this is the first time this phenomenon has occurred in any non-photosynthetic bacterium, which could have far-reaching implications for understanding bacteria as a whole: organisms that make up about 15% of the matter. alive on Earth.
“Our study opens the door to investigating circadian rhythms between bacteria,” says circadian rhythm researcher Antony Dodd of the John Innes Center in the UK.
Now that we have established that non-photosynthetic bacteria can tell us the time we need to find out the processes in bacteria that cause these rhythms and understand why having a rhythm gives bacteria an advantage.
For now, the team speculates that circadian rhythms may be somehow regulated by a transcription-translation feedback system or may be related to metabolic cycles.
It is also not known whether a form of general “master clock” can somehow control B. subtilisCircadian time, as suggested by humans, although the team emphasizes that it is a possibility.
“It will be informative to investigate whether temperature and light are inputs for a primary pacemaker or whether B. subtilis it could have multiple oscillators, as described for a variety of unicellular and multicellular organisms, “the authors write in their paper.
“It simply came to our notice then B. subtilis it could have either a main oscillator or one or more downstream oscillators, which are coupled and driven by a main pacemaker. “
In any case, the ramifications of a 24-hour body clock of bacteria could have huge ramifications – not only in terms of scientific understanding of bacterial biology, but also in its potential use in biomedical sciences, agriculture, industry and beyond. .
“Bacillus subtilis is used in various applications from the production of laundry detergents to crop protection … [and] human and animal probiotics “, says bioengineer Ákos Kovács from the Technical University of Denmark.
“Thus, the design of a biological clock in this bacterium will culminate in various biotechnological areas.”
The findings are reported in Scientific advances.