In a first discovery of its kind, scientists found 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 our cells, influencing virtually all the processes in our bodies, influencing when we sleep and get up, plus the functioning of our metabolism and cognitive processes.
This internal timing, which revolves around a 24-hour cycle, is driven by our circadian clock, and the same nuclear phenomenon has also been observed in many other types of organisms, including animals, plants and fungi.
For a long time, however, it has been unclear whether bacteria in general are also subject to the prescriptions of circadian rhythms.
The phenomenon has been shown in photosynthetic bacteria, which use light to produce chemical energy, but whether other types of bacteria also possess circadian clocks remains a mystery – until now.
“We first discovered that non-photosynthetic bacteria can tell the time,” explains chronobiologist Martha Merrow of Ludwig Maximilian University of Munich.
“They adapt their molecular action to the time of day by reading the cycles in light or in the temperature environment.”
In a new study, Merrow and fellow researchers investigated Bacillus subtilis, a hardy, well-studied bacterium found in the soil and digestive tract of many animals, including humans.
While B. subtilis is not photosynthetic, it is sensitive to light thanks to photoreceptors, and previous observations of the microbes have suggested that gene activity and biofilm formation processes may follow a daily cycle in response to environmental indications, perhaps based on light levels or temperature changes.
To investigate, the researchers measured the bacterium’s gene expression activity 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, indicating processes of seduction in a circadian clock.
When exposed to constant darkness, the cycle still existed B. subtilis, although the period extended, not strictly after a 24-hour cycle without the light signal going off.
In another experiment, the researchers experimented with temperature cycles, which is another way to stimulate changes in heat between day and night.
Again, the expression of ytvA decreased and flowed as the temperature circulated between 25 hours at 25.5 ° C (77.9 ° F) and 12 hours at 28.5 ° C (83.3 ° F), and as with light, the cycle continued in a free-running state. experiment (not synchronized with environmental instructions) although it is longer.
If we summarize all the results, the researchers come to the conclusion B. subtilis has a circadian clock, displayed by free-running circadian rhythms and systematic compassion to environmental cues, known as timer cycles.
Although the findings for the time being concern only one bacterial species, it is the first time that this phenomenon has occurred in non-photosynthetic bacteria, which could have major implications for our understanding of bacteria as a whole: organisms that make up about 15 percent of living matter on earth.
“Our study opens doors to investigate circadian rhythms about bacteria,” says researcher Antony Dodd of the circadian rhythms of the John Innes Center in the UK.
“Now that we have determined that non-photosynthetic bacteria can determine the time required to find out the processes in bacteria that cause these rhythms and understand why a rhythm gives bacteria an advantage.”
For now, the team speculates the circadian rhythms may be somehow regulated by a transcription-translation feedback system, or it may be linked to metabolic cycles.
It is also unknown whether one form of overall ‘main clock’ can somehow control B. subtiliss circadian time attitude, as suggested by humans, although the team points out that this is a possibility.
“It will be instructive to examine whether temperature and light input are up to one master pacemaker, or B. subtilis may have multiple oscillators, as described for a variety of single-celled and multicellular organisms, ‘the authors write in their paper.
“It is also possible that B. subtilis may have a master oscillator or one or more downstream oscillators connected and entrained by a pacemaker. ‘
In any case, the effects of a 24-hour body clock in bacteria can have major consequences – not only in terms of the scientific understanding of bacterial biology, but also its potential use in biomedical science, agriculture, industry and beyond.
“Bacillus subtilis is used in various applications, from the production of detergents to crop protection … [and] human and animal probiotics, ”says bioengineer Ákos Kovács from the Technical University of Denmark.
“The construction of a biological clock in this bacterium will result in diverse biotechnological areas.”
The findings are presented in Scientific progress.