Pollard E C, Grady L J
Biophys J. 1967 Mar;7(2):205-13. doi: 10.1016/S0006-3495(67)86584-6.
Cells of Escherichia coli have been successfully banded in CsCl density gradients and a portion of the population reclaimed in a viable state. Differentiation between two strains of this organism in a CsCl density gradient has been demonstrated also. Several studies were undertaken to see whether differences could be detected between two samples of cells of the same strain which had been subjected to different conditions. The results were as follows: (a) Introduction of a heavy label (5-bromouracil) into the DNA during a 90 minute period did not produce an observable change in cell density. (b) Removal of a required amino acid from the growth medium of an E. coli auxotroph resulted in an increase in both the density and heterogeneity of the cells. (c) Exposure of cells to 27 kr of gamma radiation, followed by a period during which portions of both DNA and RNA were lost, yielded two distinct bands, one at the normal position in the gradient and the other shifted to a lighter region.
大肠杆菌细胞已成功在氯化铯密度梯度中进行分带，并且一部分细胞群体以存活状态回收。在氯化铯密度梯度中也已证明该生物体的两种菌株之间存在差异。进行了多项研究，以观察在经历不同条件的同一菌株的两个细胞样本之间是否能检测到差异。结果如下：(a) 在90分钟内将重标记物（5-溴尿嘧啶）引入DNA中，未产生可观察到的细胞密度变化。(b) 从大肠杆菌营养缺陷型的生长培养基中去除必需氨基酸，导致细胞密度和异质性增加。(c) 将细胞暴露于27千伦琴的伽马射线，随后经历一段DNA和RNA部分丢失的时期，产生了两条明显的带，一条在梯度中的正常位置，另一条移至较轻区域。
