Meikle A J, Reed R H, Gadd G M
Department of Biological Sciences, University of Dundee, UK.
J Gen Microbiol. 1988 Nov;134(11):3049-60. doi: 10.1099/00221287-134-11-3049.
In the presence of a suitable carbon source, whole cells and protoplasts of Saccharomyces cerevisiae synthesized glycerol as a compatible organic solute in response to increased external osmotic pressure. Boyle-van't Hoff plots showed that protoplasts, and non-turgid cells, exhibited a linear relationship between volume and the external osmotic pressure (i.e. they behaved as near-ideal osmometers), and that both protoplasts and cells have a component which is not osmotically responsive--the non-osmotic volume (NOV). Glycerol levels in whole cells and protoplasts were elevated by increased external osmotic pressure over a similar time-scale to the period of exponential cell growth, reaching a maximum value at 6-12 h and declining thereafter. This suggests that the restoration of turgor pressure in whole cells was not the sole regulator of glycerol accumulation. Stationary phase whole cells had negligible levels of intracellular glycerol after growth in a medium of raised osmotic pressure. However, intracellular trehalose synthesis in these cells began earlier and reached a higher maximum level than in basal medium. Once exponential growth had stopped, cell turgor and internal osmotic pressure decreased somewhat. These new, lower values may be determined by the extent of trehalose accumulation in stationary phase cells.
在有合适碳源存在的情况下，酿酒酵母的完整细胞和原生质体会响应外界渗透压升高而合成甘油作为一种相容性有机溶质。玻意耳 - 范特霍夫图表明，原生质体和非膨胀细胞在体积与外界渗透压之间呈现线性关系（即它们表现得近乎理想渗透压计），并且原生质体和细胞都有一个对渗透压无响应的组分——非渗透体积（NOV）。在与指数生长期相似的时间尺度内，外界渗透压升高会使完整细胞和原生质体中的甘油水平升高，在6 - 12小时达到最大值，随后下降。这表明完整细胞中膨压的恢复并非甘油积累的唯一调节因素。在渗透压升高的培养基中生长后，稳定期完整细胞内甘油水平可忽略不计。然而，这些细胞内海藻糖的合成比在基础培养基中开始得更早，且达到的最高水平更高。一旦指数生长停止，细胞膨压和内部渗透压会有所下降。这些新的较低值可能由稳定期细胞中海藻糖积累的程度决定。
