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Updated: Jul 20, 2025

In Vitro Bioluminescence Assay to Characterize Circadian Rhythm in Mammary Epithelial Cells
Published on: September 28, 2017
The circadian clock of the bacterium B. subtilis evokes properties of complex, multicellular circadian systems
Francesca Sartor1, Xinming Xu2,3, Tanja Popp1
1Institute of Medical Psychology, Medical Faculty, LMU Munich, Munich, Germany.
Abstract:
Circadian clocks are pervasive throughout nature, yet only recently has this adaptive regulatory program been described in nonphotosynthetic bacteria. Here, we describe an inherent complexity in the Bacillus subtilis circadian clock. We find that B. subtilis entrains to blue and red light and that circadian entrainment is separable from masking through fluence titration and frequency demultiplication protocols. We identify circadian rhythmicity in constant light, consistent with the Aschoff's rule, and entrainment aftereffects, both of which are properties described for eukaryotic circadian clocks. We report that circadian rhythms occur in wild isolates of this prokaryote, thus establishing them as a general property of this species, and that its circadian system responds to the environment in a complex fashion that is consistent with multicellular eukaryotic circadian systems.
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