Lattice Gas Model for Budding Yeast: A New Approach for Density Effects
Lattice Gas Model for Budding Yeast: A New Approach for Density Effects
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DOI：
10.1016/j.procs.2014.05.024
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
K. Tainaka;T. Ushimaru;Toshiyuki Hagiwara;J. Yoshimura
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文献类型：
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作者：
K. Tainaka;T. Ushimaru;Toshiyuki Hagiwara;J. Yoshimura
培养基中的酵母在早期呈指数增长，但最终停止生长。人口增长的饱和是由于“密度效应”。出芽的酵母，酿酒酵母，已知表现出年龄依赖的细胞分裂。不生育的子细胞比母细胞有更长的世代时间，因为子细胞需要成熟期。迄今为止，对指数增长期的研究已经大量积累，但对密度效应的阶段依赖性了解甚少。在这里，我们提出了密度效应的“体内”研究，应用晶格气体模型来探索年龄结构动力学。然而，解基本方程是困难的，因为它们有无数的变量和参数。基本方程由几个变量和参数较少的简化模型构建而成。将这些简化模型与实验数据进行比较，报告了阶段依赖密度效应的两个发现：1)出生率下降悖论（PDB）和2)高龄母亲集体自杀。这些事件发生在密度效应的早期，具有突发性和暂时性。母女模式导致PDB。也就是说，当人口出生率下降时，女孩的比例突然增加。此外，我们发现酵母群体的平均年龄在拐点突然下降。这意味着老年母亲的大量凋亡。我们对密度效应的研究结果表明，存在几种特异性抑制种群生长的“信息素”。
Yeasts in culture media grow exponentially in early period but eventually stop growing. The saturation of population growth is due to “density effect”. The budding yeast, Saccharomyces cerevisiae, is known to exhibit an age-dependent cell division. Daughter cell, which gives no birth, has longer generation time than mother, because daughter needs maturing period. So far, investigations in exponential growth period have been intensively accumulated, but very little is known for the stage dependence of density effect. Here we present an “in vivo” study of density effect, applying a lattice gas model to explore the age-structure dynamics. It is, however hard to solve basic equations, because they have an infinite number of variables and parameters. The basic equations are constructed from several simplified models which have few variables and parameters. These simplified models are compared with experimental data to report two findings for stage-dependent density effect: 1) paradox of decline birthrate (PDB), and 2) mass suicide of aged mothers. These events suddenly and temporarily occur at early stage of density effect. The mother-daughter model leads to PDB. Namely, when the birthrate of population is decreased, then the fraction of daughter is abruptly increased. Moreover, we find the average age of yeast population suddenly decreases at the inflection point. This means the mass apoptosis of aged mothers. Our results for density effect imply the existence of several types of “pheromones” that specifically inhibit the population growth.