Low temperature nullifies the circadian clock in cyanobacteria through Hopf bifurcation

Research Highlight

Chilled bacteria lose their rhythm

© NNehring/E+/Getty

© NNehring/E+/Getty

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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  1. PNAS 114, 5641–5646 (2017). doi: 10.1073/pnas.1620378114
Institutions Share
School of Design / Graduate School of Design / Faculty of Design, Kyushu University, Japan 0.42
Department of Electrical Engineering and Bioscience, Waseda University, Japan 0.25
Department of Information Sciences, Ochanomizu University, Japan 0.17
Division of Biological Science, Nagoya University, Japan 0.08
Institute for Advanced Research (IAR), Nagoya University, Japan 0.08