Researchers discover the importance of aligning the biological clock with day-night cycles

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Researchers discover importance of aligning biological clock with day-night cycles

New research provides a vivid example of the importance of keeping the internal biological clock aligned with the external environment so that processes occur at the right time of day. Credit: Golden Lab, UC San Diego

Timing is everything. A new example supporting the old adage has been found in connection with systems regulated by biological clocks.

Research on circadian rhythms, our 24-hour internal patterns that affect waking and metabolic cycles, has shown that timing is essential for human health. When our internal circadian clocks and activities are out of step with the natural day-night cycle – for example, irregular shift work, jet lag and poor sleep-wake habits – we increase our risk of illness due to poor estimation of important biological processes. But the genetics behind these mechanisms is not well established.

Today, scientists at the University of California, San Diego, who study photosynthetic bacteria called cyanobacteria, or “blue algae,” have identified the roots of behavior regulated by the circadian clock.

The results, chaired by Arnaud Taton, associate scientist of the project in the Biological Sciences Division and lead authors James and Susan Golden, are published in Nature Communications.

“I think this document demonstrates the importance of matching internal biological time with environmental time,” said Susan Golden, distinguished professor at the University of San Diego in California, director of the Center for Circadian Biology and lead author of the document. ‚ÄúThere are many human diseases in which people are out of alignment with their environment. This can result from habits such as too much light at night, eating at odd times of the day, and not sleeping regularly. In cyanobacteria, this makes a very big difference for the alignment of biological time and the time of the external environment. “

Researchers discover importance of aligning biological clock with day-night cycles

The columns show samples of cyanobacteria taken at different times of the day and incubated with DNA which, if absorbed and incorporated, allows them to grow on a medium containing antibiotics. Higher green growth in the column shows that more cells have taken up the DNA. The center, twilight and early night samples absorb DNA thousands of times better than the dawn samples (left and right edges). Credit: Golden Lab, UC San Diego

Scientists know that when researching new genes, bacteria incorporate DNA from the environment. These processes ensure that there is raw material to generate genetic variation, this is how species evolve. However, the details of this confusing process are only understood in a few organizations. The ability to absorb DNA is generally tightly regulated, suggesting to scientists that it would be detrimental to the body to indiscriminately capture foreign genes.

In the new study, researchers identified the mechanisms of DNA absorption in the cyanobacterium Synechococcus elongatus and discovered that the internal circadian clocks in their cells prevent DNA absorption early in the day and improve the process early in the day. the night. They predicted that the clock-mediated expression of certain dark-induced genes at dusk is essential for absorbing DNA from the environment. They found that when darkness occurs when the cells’ internal clock tells them that twilight, DNA uptake and incorporation increase dramatically. On the other hand, darkness at times which do not correspond to the time of the internal clock fails to increase the capture and incorporation of DNA.

As to why early DNA absorption is discouraged and late absorption is improved, scientists are not entirely sure. They are testing hypotheses such as whether it can be useful to avoid absorbing potentially harmful DNA when viruses are more prevalent, which occurs in some environments during the day.

“This study provides a vivid example of the importance of keeping the internal biological clock aligned with the external environment so that processes occur at the right time of day,” say the researchers.


A key switch in biological clocks


More information:
Arnaud Taton et al, The circadian clock and darkness control the natural competence of cyanobacteria, Nature Communications (2020). DOI: 10.1038 / s41467-020-15384-9

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University of California – San Diego

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