PACKER E L, INGRAHAM J L, SCHER S
J Bacteriol. 1965 Mar;89(3):718-24. doi: 10.1128/jb.89.3.718-724.1965.
Packer, Elliot L. (University of California, Davis), John L. Ingraham, and Stanley Scher. Factors affecting the rate of killing of Escherichia coli by repeated freezing and thawing. J. Bacteriol. 89:718-724. 1965.-Repeated freezing and thawing of cultures of Escherichia coli grown in a minimal medium and frozen in the same medium without carbon source resulted in a linear decrease in the log of the number of surviving cells as a function of the number of freeze-thaw cycles. The slope of this curve, which can be determined accurately, is an index of susceptibility of a culture to death by freezing and thawing. The effect of the physiological state of the culture on the killing rate was determined. Contrary to previous reports, the phase of growth, the state of aerobiosis, and the density of the culture had no effect on the degree of susceptibility to death by freezing and thawing. However, presence of spent growth medium (a filtrate of a stationary culture) in the freezing medium protected cells against death by freezing and thawing. Protection by spent growth medium is effective at high dilutions (1:10(5)), and is lost if spent growth medium is heated in the presence of alkali. It is suggested that the protection afforded by spent growth medium accounts for differences between our results and those reported in the literature.
帕克，埃利奥特·L.（加利福尼亚大学戴维斯分校）、约翰·L.英格拉姆和斯坦利·舍尔。反复冻融对大肠杆菌杀灭率的影响因素。《细菌学杂志》89:718 - 724。1965年。——在基本培养基中生长并在无碳源的相同培养基中冷冻的大肠杆菌培养物，反复冻融导致存活细胞数的对数随冻融循环次数呈线性下降。这条曲线的斜率（可精确测定）是培养物对冻融死亡敏感性的指标。测定了培养物生理状态对杀灭率的影响。与之前的报道相反，生长阶段、需氧状态和培养物密度对冻融死亡的敏感程度没有影响。然而，冷冻培养基中存在用过的生长培养基（静止培养物的滤液）可保护细胞免受冻融死亡。用过的生长培养基在高稀释度（1:10⁵）时具有保护作用，若在碱性条件下加热用过的生长培养基则失去保护作用。有人认为，用过的生长培养基提供的保护作用解释了我们的结果与文献报道结果之间的差异。
