In a first discovery of its kind, scientists have discovered that a species of non-photosynthetic bacteria is regulated by the same circadian rhythms that dominate so many other life forms.
In humans, our circadian rhythms act as a kind of biological clock in cells, controlling virtually every process in our body, influencing when we sleep and increase, as well as the functioning of our metabolism and cognitive processes.
This maintenance 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 has not been possible to know 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 as to whether other types of bacteria also possess circadian clocks, it has long been a mystery, until now.
“We have found for the first time that non-photosynthetic bacteria can know the time,” 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 around the temperature.”
In a new study, Merrow and other researchers examined it Bacillus subtilis, a resistant and well-studied bacterium found in the soil and gastrointestinal tract of many animals, including humans.
While B. subtilis it is not photosynthetic, it is sensitive to light thanks to photoreceptors and previous observations of the microbe have given clues that its gene activity and biofilm formation processes could follow a daily cycle in response to environmental cues, perhaps based on light levels or temperature changes.
To investigate, the researchers measured the gene expression activity of the bacterium in cultures exposed to constant darkness or an alternating 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 drag processes in a circadian clock.
When subjected to constant darkness, the cycle still existed in B. subtilis, although the period was extended, not strictly following a 24-hour cycle without the light signal being turned off.
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 flowed as temperatures circulated between 12 hours at 25.5 ° C (77.9 ° F) and 12 hours at 28.5 ° C (83.3). ° F) and, as with light, the cycle persisted in a free-running experiment (not synchronized with environmental cues) although with a longer period.
Taking all the results, the researchers conclude B. subtilis has a circadian clock, exhibited by circadian rhythms of free running and systematic dragging at environmental cues known as zeitgeber cycles.
Although the findings only belong to one bacterial species for now, it is the first time this phenomenon has occurred in non-photosynthetic bacteria, which could have major implications for our understanding of bacteria as a whole: organisms representing about 15 percent of living matter on Earth.
“Our study opens doors to investigate circadian rhythms among bacteria,” says circadian rhythm researcher Antony Dodd of the John Innes Center in the UK.
“Now that we’ve established that non-photosynthetic bacteria can indicate the time we need to know the processes of bacteria that cause these rhythms to occur and understand why having a rhythm gives bacteria an advantage.”
For now, the team speculates that circadian rhythms may be regulated in some way by a transcriptional translation feedback system or be related to metabolic cycles.
It is also unknown whether a form of general “master clock” can be controlled in any way B. subtilisCircadian weather, as has been suggested in humans, although the team points out that it is a possibility.
“It will be informative to investigate whether temperature and light are inputs for a master pacemaker or whether B. subtilis they can have multiple oscillators, as described for various unicellular and multicellular organisms, ”the authors write in their article.
“It is also possible that B. subtilis it may have a master oscillator or one or more downstream oscillators that are coupled and rooted by a main pacemaker. “
In any case, the ramifications of a 24-hour body clock in bacteria could have enormous ramifications, not only in terms of scientific understanding of bacterial biology, but also in terms of its potential use in biomedical sciences, agriculture. , industry and beyond.
“Bacillus subtilis It is used in various applications, from the production of laundry detergents to crop protection … [and] human and animal probiotics, ”says bioengineer Ákos Kovács of the Technical University of Denmark.
“Thus, engineering a biological clock in this bacterium will culminate in several biotechnological areas.”
The findings are reported in Scientific advances.