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Stabilité du rythme circadien des cyanobactéries :
Investigation d'un couplage entre oscillateurs

Abstract : The circadian clock is a self-sustained biological clock that can be found in many organisms such as mammals, insects, plants, and even cyanobacteria. This rhythm allows living organisms to coordinate their metabolic and behavioural activities with the Earth's daily rotation. The free-running period of this clock is close to 24h h.
The cyanobacteria Synechococcus elongatus sp. PCC7942 is the simplest organism that has this circadian clock. And in spite of cellular division (up to 3 divisions per 24 h), the oscillations persist among a population of bacteria. Moreover, single-cell experiments showed that the oscillations were persisting with a correlation time of several months.
We thus raised the question of the origin of such a robust oscillator. Indeed, the cyanobacteria are submitted to various sources of noise, and in spite of these fluctuations, the oscillations remain robust. We therefore investigate the potential coupling between oscillators, which could reinforce the stability of oscillations.
By using strains carrying a luciferase reporter, we access to the circadian clock of cyanobacteria. We also used a theoretical model of week interaction between oscillators, this model taking into account the phase diffusion of oscillations. By confronting experimental measures with numerical simulations, we managed to estimate an upper limit to the potential coupling strength between oscillators. By comparing the phase diffusion constant with the coupling strength, we showed that the robustness of the circadian clock of cyanobacteria is a built-in property.
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Contributor : Malika Amdaoud <>
Submitted on : Thursday, October 11, 2007 - 12:16:07 PM
Last modification on : Tuesday, September 11, 2018 - 11:00:02 AM
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  • HAL Id : tel-00178482, version 1




Malika Amdaoud. Stabilité du rythme circadien des cyanobactéries :
Investigation d'un couplage entre oscillateurs. Biophysique []. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00178482⟩



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