Institute for Biochemistry and Biology, University of Potsdam, 14469 Potsdam, Germany.
Proc Natl Acad Sci U S A. 2010 Mar 2;107(9):4236-41. doi: 10.1073/pnas.0908725107. Epub 2010 Feb 16.
Complex dynamics, such as population cycles, can arise when the individual members of a population become synchronized. However, it is an open question how readily and through which mechanisms synchronization-driven cycles can occur in unstructured microbial populations. In experimental chemostats we studied large populations (>10(9) cells) of unicellular phytoplankton that displayed regular, inducible and reproducible population oscillations. Measurements of cell size distributions revealed that progression through the mitotic cycle was synchronized with the population cycles. A mathematical model that accounts for both the cell cycle and population-level processes suggests that cycles occur because individual cells become synchronized by interacting with one another through their common nutrient pool. An external perturbation by direct manipulation of the nutrient availability resulted in phase resetting, unmasking intrinsic oscillations and producing a transient collective cycle as the individuals gradually drift apart. Our study indicates a strong connection between complex within-cell processes and population dynamics, where synchronized cell cycles of unicellular phytoplankton provide sufficient population structure to cause small-amplitude oscillations at the population level.
当种群的个体成员变得同步时，就会出现复杂的动态，如种群周期。然而，在无结构的微生物种群中，同步驱动的周期通过哪些机制以及多快能够发生，这仍然是一个悬而未决的问题。在实验恒化器中，我们研究了显示出有规律、可诱导和可重复的种群波动的单细胞浮游植物的大型种群（>10^9 个细胞）。细胞大小分布的测量表明，有丝分裂周期的进展与种群周期同步。一个既能解释细胞周期又能解释种群水平过程的数学模型表明，周期的出现是因为个体细胞通过共同的营养池相互作用而变得同步。通过直接操纵营养供应进行外部干扰会导致相位重置，揭示内在波动，并产生一个短暂的集体周期，因为个体逐渐漂移开。我们的研究表明，复杂的细胞内过程和种群动态之间存在很强的联系，单细胞浮游植物的同步细胞周期为种群水平上的小幅度波动提供了足够的种群结构。
