In their first discovery, scientists found that a type of non-photosynthetic bacterium 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 our cells, controlling virtually all processes in our bodies, influencing when we sleep and get up, plus the functioning of our metabolism and cognitive processes.
This internal measurement of time, which revolves around a 24-hour cycle, is driven by our circadian clock, and the same nucleus is observed in many other species of organisms, including animals, plants and fungi.
However, it has not been clear for a long time whether bacteria in general are also subject to the dictates of circadian rhythms.
The phenomenon has been demonstrated in photosynthetic bacteria that use light to produce chemical energy, but whether other types of bacteria also have circadian clocks has long remained a mystery.
“For the first time, we discovered that non-photosynthetic bacteria can determine time,”
“They adapt their molecular work to the time of day by reading the cycles in light or in the temperature environment.”
In a new study, Merow and fellow researchers investigated Bacillus subtilis, a hardy, 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 suggest that its genetic activity and biofilm formation processes may follow a daily cycle in response to environmental signals, perhaps based on light levels. or temperature changes.
To investigate, the researchers measured the activity of bacterial gene expression in cultures exposed to either constant darkness or an alternating daily cycle of 12 hours of light, followed by 12 hours of darkness.
In the alternating light / darkness 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 processes of conquest in a circadian clock.
When it was subjected to constant darkness, the cycle still existed through B. subtilis, although the period is prolonged without 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 changes in heat between day and night.
Again, ytvA expression decreases and proceeds when temperatures cycle between 12 hours at 25.5 ° C (77.9 ° F) and 12 hours at 28.5 ° C (83.3 ° F) and, as in light , the cycle continues in a free-running experiment (not synchronized with environmental signals), albeit with a longer period.
Taking all the results together, the researchers conclude B. subtilis there is a circadian clock exposed by freely circulating circadian rhythms and systematic attraction to ecological signals known as Zeitgeber cycles.
While the findings so far relate to only one bacterial species, this phenomenon is first seen in some non-photosynthetic bacteria, which can have huge implications for our understanding of bacteria in general: organisms that make up approximately 15 percent of living matter on Earth.
“Our study opens the door to the study of circadian rhythms in bacteria,” said circadian rhythm researcher Anthony Dodd of the John Ince Center in the United Kingdom.
“Now that we’ve found that non-photosynthetic bacteria can determine the time it takes us to understand the processes in bacteria that cause these rhythms, and to understand why having a rhythm gives bacteria an advantage.”
For now, the team suggests that circadian rhythms may be regulated in some way by a transcription and translation feedback system, or they may be linked to metabolic cycles.
It is also unknown whether a form of complete “master clock” can in any way control B. subtiliscircadian timekeeping, as assumed in humans, although the team indicates that this is possible.
“It will be informative to examine whether temperature and light are inputs to a main pacemaker or B. subtilis there may be multiple oscillators, as described for different unicellular and multicellular organisms, “the authors write in their report.
“It simply came to our notice then B. subtilis there may be either a main oscillator or one or more downstream oscillators that are connected and captured by a main pacemaker. “
In any case, the effects of the 24-hour body clock on bacteria can have enormous consequences – not only in terms of the scientific understanding of bacterial biology, but also in its potential use in biomedical science, agriculture, industry and beyond.
“Bacillus subtilis is used in various applications from the production of detergents to plant protection … [and] human and animal probiotics, “says bioengineer Akos Kovacs of the Technical University of Denmark.
“In this way, the design of a biological clock in this bacterium will be completed in various biotechnological fields.”
The findings were reported in Scientific progress.