Biological complexity: some bacteria have circadian rhythm (Introduction)

by David Turell , Friday, February 12, 2021, 05:12 (1168 days ago) @ David Turell

In the gut:

https://bigthink.com/surprising-science/gut-bacteria-circadian-rhythm?rebelltitem=1#reb...

"...a new study, published in Science Advances, that found the bacterium Bacillus subtilis is run by its own circadian rhythms.

"Also known as "grass bacillus," B. subtilis thrives in the gastrointestinal tracts of humans as well as grass-feeding ruminants. You can easily and cheaply purchase bottles of this bacterium as a probiotic due to its supposed immune system-boosting properties. The strain is found in soil, though you probably want to secure it by other means, making it a favorite of supplement companies.

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"For this study, the European research team chose B. subtilis thanks to previous observations that, like humans, it seems to follow a 24-hour circadian clock. It also responds to red and blue lights (again, like humans), causing the researchers to believe that it entrains to environmental conditions. The team discovered this by enzymatically inducing bioluminescence in order to stare into this mysterious world.

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"'We've found for the first time that non-photosynthetic bacteria can tell the time. They adapt their molecular workings to the time of day by reading the cycles in the light or in the temperature environment."

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"Rather than only responding to light and dark, B. subtilis takes cues from temperature drops, hinting at a circadian rhythm.

"Although bacteria comprise 15 percent of all living matter, the team notes that circadian clocks have not been identified in nonphotosynthetic bacteria—until now. They note that bacterium such as Rhodospirillum rubrum displays rhythmic processes such as enzymatic activity yet has no apparent circadian clock.

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"'Our study opens doors to investigate circadian rhythms across bacteria. Now that we have established that bacteria can tell the time we need to find out the processes that cause these rhythms to occur and understand why having a rhythm provides bacteria with an advantage."

"Understanding the survival methods of bacterium clues us in on the long, slow process of evolution. While this new discovery does not state the purpose of the circadian clock in B. subtilis, it opens up a new line of research for one of the most perplexing components of human biology: our guts."

Comment: Hopefully we will find a purpose for this. Night and day on Earth sets up this requirement but why in the darkness of the gut?