Low temperature nullifies the circadian clock in cyanobacteria through Hopf bifurcation

Chilled bacteria lose their rhythm

23 November 2017

Cyanobacteria’s daily rhythms come to a halt when it is cooled, but are revived by pulses of heat.

Circadian rhythms are biological processes that repeat over a roughly 24-hour cycle, such as sleep and digestion, but the rhythmicity disappears in many organisms if they get too cold. A Japanese team including researchers from Kyushu University cooled a test tube containing KaiC proteins — which regulate a daily surge in gene expression in cyanobacteria — and adenosine triphosphate (ATP) molecules.

They measured the proportion of KaiC that had reacted with ATP every two hours. As the temperature fell from 29.9°C, the reaction peaks became smaller and less regular, and disappeared below 19°C.

Applying periodic 30°C warm pulses regenerated tiny but regular oscillations in KaiC activity below 19°C, which suggests that KaiC could maintain the circadian rhythm of cyanobacteria during cold periods by responding to periodical changes in their surroundings.

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References

1. PNAS 114, 5641–5646 (2017). doi: 10.1073/pnas.1620378114