Schall B F, Marathe G V, Ghosh B K
J Bacteriol. 1981 Apr;146(1):391-7. doi: 10.1128/jb.146.1.391-397.1981.
The plasmolytic response of Bacillus licheniformis 749/C cells to the increasing osmolarity of the surrounding medium was quantitated with stereological techniques. Plasmolysis was defined as the area (in square micrometers) of the inside surface of the bacterial wall not in association with bacterial membrane per unit volume (in cubic micrometers) of bacteria. This plasmolyzed surface area was zero when the cells were suspended in a concentration of sucrose solution lower than 0.5 M, but increased linearly when the sucrose molarity rose above 0.5 M, reaching a plateau value of 3.61 micrometers2/micrometers3 in 2 M sucrose. In contrast, when the bacterial cells were treated with lysozyme plasmolysis increased abruptly from 0.06 micrometers2/micrometers3 in 0.75 M sucrose to 4.09 micrometers2/micrometers3 in 1 M sucrose. When the time of exposure was prolonged, the degree of plasmolysis increased gradually for the duration of the experiment (30 min) after exposure to 1 M sucrose without lysozyme, whereas with lysozyme plasmolysis reached a maximum (4.09 micrograms2/micrometers3) in 2 to 5 min. The examination of ultrastructure showed that the protoplast bodies of lysozyme-treated cells in 1 M sucrose and untreated cells in 2 M sucrose are maximally retracted from the intact wall of the bacteria; hardly any retraction of protoplasts could be seen for untreated cells in 1 M sucrose. The data suggest that the B. licheniformis cells are isoosmotic to 800 to 1,100 mosM solutions, but are able to withstand much greater osmotic pressure with no signs of plasmolysis because the cell wall and the plasma membrane are held in close association, perhaps by a covalent bond. It is likely that lysozyme weakens this bond by degradation of the peptidoglycan layer. Cellular autolysis also weakens this wall-membrane association.
利用体视学技术对嗜热栖热放线菌749/C细胞对周围培养基渗透压升高的质壁分离反应进行了定量分析。质壁分离定义为每单位体积（立方微米）细菌中，细菌细胞壁内表面与细菌膜不相连的面积（平方微米）。当细胞悬浮在浓度低于0.5M的蔗糖溶液中时，这种质壁分离表面积为零，但当蔗糖摩尔浓度升至0.5M以上时呈线性增加，在2M蔗糖中达到3.61平方微米/立方微米的平台值。相比之下，当用溶菌酶处理细菌细胞时，质壁分离从0.75M蔗糖中的0.06平方微米/立方微米突然增加到1M蔗糖中的4.09平方微米/立方微米。当暴露时间延长时，在不添加溶菌酶的情况下，暴露于1M蔗糖后，在实验持续时间（30分钟）内质壁分离程度逐渐增加，而添加溶菌酶后，质壁分离在2至5分钟内达到最大值（4.09微克/立方微米）。超微结构检查表明，1M蔗糖中经溶菌酶处理的细胞和2M蔗糖中未处理的细胞的原生质体从细菌完整壁中最大程度地收缩；在1M蔗糖中未处理的细胞几乎看不到原生质体的收缩。数据表明，嗜热栖热放线菌细胞与800至1100 mosM溶液等渗，但能够承受更大的渗透压而无质壁分离迹象，因为细胞壁和质膜紧密相连，可能是通过共价键。溶菌酶可能通过降解肽聚糖层削弱这种键。细胞自溶也会削弱这种壁-膜结合。
