Arnold W N, Lacy J S
J Bacteriol. 1977 Aug;131(2):564-71. doi: 10.1128/jb.131.2.564-571.1977.
Bakers' yeast (Saccharomyces cerevisiae) was equilibrated with distilled water and then packed into standardized pellets by centrifugation. The fractional space (S value) that was accessible to passive permeation was probed with a variety of mono- and divalent salts, mono- and disaccharides, polyols, substrates and products of beta-fructofuranosidase (EC 3.2.1.26) and acid phosphatase (EC 3.1.3.2), and a cross-linked polymer of sucrose (Ficoll 400). A simple but very reproducible method was developed to measure pellet volume. At the limit of zero osmolality for bathing medium, the interstitial space was 0.223 ml/ml of pellet, and the aqueous volume of cell envelopes was 0.117 ml/ml of pellet. Thus the cell envelope for this yeast, under these conditions, was approximately 15% of the total cell volume. At a finite osmolality, the space in a yeast pellet that was accessible to salt was accounted for by the sum of initial interstitial space, the volume of the cell envelopes, and the volume of water abstracted from the cells by osmosis. Plots of S value versus osmolality were linear for uncharged probes and curvilinear for all salts. When Ficoll and potassium thiocyanate were presented to the yeast in admixture, the S values for the salt increased continuously over the range of osmolality studied. However, the S values for Ficoll 400 (which did not penetrate the cell wall) were lower by an amount equilivalent to the cell envelopes; they increased in parallel with the S curve for salt up to 1.15 osmol/kg and then plateaued. The results support the concept of incipient plasmolysis at 1.15 osmol/kg, and the separation of protoplasm from the cell wall is indicated with more concentrated solutions. Such cells were still viable if slowly diluted in distilled water, but they were injured by the shock of rapid dilution. However, shocking the cells did not release beta-fructofuranosidase into the medium. The complete accessibility of salts toward killed cells was demonstrated with yeast that had been pretreated with heat, organic solvents, or glutaraldehyde.
将面包酵母（酿酒酵母）用蒸馏水平衡，然后通过离心将其装入标准化的小球中。用多种单价和二价盐、单糖和双糖、多元醇、β-呋喃果糖苷酶（EC 3.2.1.26）和酸性磷酸酶（EC 3.1.3.2）的底物和产物以及蔗糖交联聚合物（聚蔗糖400）探测被动渗透可及的分数空间（S值）。开发了一种简单但非常可重复的方法来测量小球体积。在培养基渗透压为零的极限情况下，间质空间为0.223毫升/毫升小球，细胞膜的水体积为0.117毫升/毫升小球。因此，在这些条件下，这种酵母的细胞膜约占细胞总体积的15%。在有限的渗透压下，酵母小球中盐可及的空间由初始间质空间、细胞膜体积和通过渗透从细胞中抽出的水体积之和构成。对于不带电的探针，S值与渗透压的关系图是线性的，而对于所有盐类则是曲线的。当聚蔗糖和硫氰酸钾混合加入酵母时，在所研究的渗透压范围内，盐的S值持续增加。然而，聚蔗糖400（未穿透细胞壁）的S值比细胞膜所占的量低；它们与盐的S曲线平行增加，直至1.15渗透压/千克，然后趋于平稳。结果支持在1.15渗透压/千克时开始质壁分离的概念，更浓的溶液表明原生质与细胞壁分离。如果在蒸馏水中缓慢稀释，这些细胞仍然存活，但它们会因快速稀释的冲击而受损。然而，冲击细胞并不会将β-呋喃果糖苷酶释放到培养基中。用热、有机溶剂或戊二醛预处理过的酵母证明了盐对死细胞的完全可及性。
