Cell cycle implication on nitrogen acquisition and synchronization in Thalassiosira weissflogii (Bacillariophyceae)

Authors

  • Christophe Mocquet,

    Corresponding author
    1. CNRS, UMR 7093, LOV, Observatoire Océanologique, Villefranche/mer, France
    • UPMC, Univ Paris 06, UMR 7093, LOV, Observatoire Océanologique, Villefranche/mer, France
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  • Antoine Sciandra,

    1. UPMC, Univ Paris 06, UMR 7093, LOV, Observatoire Océanologique, Villefranche/mer, France
    2. CNRS, UMR 7093, LOV, Observatoire Océanologique, Villefranche/mer, France
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  • Amélie Talec,

    1. UPMC, Univ Paris 06, UMR 7093, LOV, Observatoire Océanologique, Villefranche/mer, France
    2. CNRS, UMR 7093, LOV, Observatoire Océanologique, Villefranche/mer, France
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  • Olivier Bernard

    1. INRIA, Biocore, Sophia Antipolis, France
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Author for correspondence: e-mail christophe.mocquet@skema.edu.

Abstract

The Michaelis–Menten model of nitrogen (N) acquisition, originally used to represent the effect of nutrient concentration on the phytoplankton uptake rate, is inadequate when other factors show temporal variations. Literature generally links diurnal oscillations of N acquisition to a response of the physiological status of microalgae to photon flux density (PFD) and substrate availability. This work describes how the cell cycle also constitutes a significant determinant of N acquisition and, when appropriate, assesses the impact of this property at the macroscopic level. For this purpose, we carried out continuous culture experiments with the diatom Thalassiosira weissflogii (Grunow) G. Fryxell & Hasle exposed to various conditions of light and N supply. The results revealed that a decrease in N acquisition occurred when a significant proportion of the population was in mitosis. This observation suggests that N acquisition is incompatible with mitosis and therefore that its acquisition rate is not constant during the cell cycle. In addition, environmental conditions, such as light and nutrient supply disrupt the cell cycle at the level of the individual cell, which impacts synchrony of the population.

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