Gray R J, Ordal Z J, Witter L D
Appl Environ Microbiol. 1977 May;33(5):1074-8. doi: 10.1128/aem.33.5.1074-1078.1977.
Thermally injured cells of Pseudomonas fluorescens were unable to produce colonies on Trypticase soy agar (TSA) after dilution with 0.1% peptone. Nutritional exigency could not be used as the criterion for this injury, since varying the composition of the plating medium had little effect on the number of colonies that developed. The injured cells had no requirement for compounds known to leak out during the heat treatment in order to recover. The cells did not exhibit injury if dilution preceded heat treatment on the plating medium, demonstrating that the heat treatment sensitized the cells to the trauma of dilution. Substitution of 0.1% peptone with growth medium as the diluent largely offset the previously observed drop in TSA count. Little difference in survival was observed when monosodium glutamate or the balance of the defined medium was used as the diluent. The diluent effect was ionic rather than osmotic. The presence of cations was important in maintaining the integrity of the injured cell, and divalent cations enhanced this protective effect. The role of these cations at the level of the cell envelope is discussed.
荧光假单胞菌经热损伤的细胞在用0.1%蛋白胨稀释后无法在胰蛋白酶大豆琼脂（TSA）上形成菌落。营养需求不能作为这种损伤的标准，因为改变平板培养基的组成对形成的菌落数量影响很小。损伤的细胞不需要已知在热处理过程中会泄漏出来的化合物来恢复。如果在平板培养基上热处理之前进行稀释，细胞不会表现出损伤，这表明热处理使细胞对稀释的损伤敏感。用生长培养基替代0.1%蛋白胨作为稀释剂在很大程度上抵消了之前观察到的TSA计数下降。当使用谷氨酸钠或限定培养基的其余部分作为稀释剂时，存活情况几乎没有差异。稀释剂的作用是离子性的而非渗透性的。阳离子的存在对于维持损伤细胞的完整性很重要，二价阳离子增强了这种保护作用。讨论了这些阳离子在细胞包膜水平上的作用。
