A model for the enhancement of fitness in cyanobacteria based on resonance of a circadian oscillator with the external light-dark cycle
A model for the enhancement of fitness in cyanobacteria based on resonance of a circadian oscillator with the external light-dark cycle
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DOI：
10.1006/jtbi.2001.2476
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发表时间：
2002-02-21
影响因子：
2
通讯作者：
Goldbeter, A
中科院分区：
文献类型：
--
作者：
Gonze, D;Roussel, MR;Goldbeter, A
最近已经在蓝细菌中证明了基于共振生物钟的健身增强[Ouyang et al.（1998）.美国国家科学院院报Sci. U.S.A.95，8660-8664]。因此，两种因昼夜节律振荡的自由运行期（FRP）不同而不同的蓝藻菌株之间的竞争导致两种菌株中的一种或另一种占据主导地位，具体取决于外部光暗（LD）循环的周期。成功应变通常是FRP最接近LD循环周期的应变。共振现象的关键重要性是观察表明，昼夜节律振荡器和LD周期之间的相位角取决于后者的周期的长度和FRP。我们通过一个理论模型来解释这些实验观察结果，该模型考虑了（i）细胞生长，（ii）假定的细胞生长抑制剂的分泌，以及（iii）控制生长和抑制剂分泌的细胞光敏昼夜节律振荡器的存在。基于先前的分析，其中相位角被认为是可自由调节的参数[Alfressel等人（2000）。J. Theor。印迹205，321-340]，我们将光敏版本的货车der Pol振荡器并入模型中以明确地表示细胞昼夜节律振荡器。以这种方式，该模型自动生成昼夜节律振荡器和LD周期之间的相位角，该相位角取决于应变的特征FRP并且随着LD周期的周期连续变化。该模型解释了不同周期LD循环夹带不同FRP菌株间竞争实验的结果。该模型进一步显示了一种菌株在LD循环中相对于另一种菌株的优势如何与以下观察结果相协调：当单独存在于培养基中时，以不同FRP为特征的两种菌株在连续光照或LD循环中显示出相同的生长动力学。理论预测的竞争结果如何取决于初始比例和不同菌株的FRPs。我们还确定了光周期的影响，并扩展分析的情况下，三个蓝藻菌株之间的竞争。
Fitness enhancement based on resonating circadian clocks has recently been demonstrated in cyanobacteria [Ouyang et al. (1998). Proc. Natl Acad. Sci. U.S.A. 95, 8660-8664]. Thus, the competition between two cyanobacterial strains differing by the free-running period (FRP) of their circadian oscillations leads to the dominance of one or the other of the two strains, depending on the period of the external light-dark (LD) cycle. The successful strain is generally that which has an FRP closest to the period of the LD cycle. Of key importance for the resonance phenomenon are observations which indicate that the phase angle between the circadian oscillator and the LD cycle depends both on the latter cycle's length and on the FRP. We account for these experimental observations by means of a theoretical model which takes into account (i) cell growth, (ii) secretion of a putative cell growth inhibitor, and (iii) the existence of a cellular, light-sensitive circadian oscillator controlling growth as well as inhibitor secretion. Building on a previous analysis in which the phase angle was considered as a freely adjustable parameter [Roussel et al. (2000). J. theor. Blot. 205, 321-340], we incorporate into the model a light-sensitive version of the van der Pol oscillator to represent explicitly the cellular circadian oscillator. In this way, the model automatically generates a phase angle between the circadian oscillator and the LD cycle which depends on the characteristic FRP of the strain and varies continuously with the period of the LD cycle. The model provides an explanation for the results of competition experiments between strains of different FRPs subjected to entrainment by LD cycles of different periods. The model further shows how the dominance of one strain over another in LD cycles can be reconciled with the observation that two strains characterized by different FRPs nevertheless display the same growth kinetics in continuous light or in LD cycles when present alone in the medium. Theoretical predictions are made as to how the outcome of competition depends on the initial proportions and on the FRPs of the different strains. We also determine the effect of the photoperiod and extend the analysis to the case of a competition between three cyanobacterial strains.