Salmeen I, Durisin A M
Mutat Res. 1981 Jun;85(3):109-18. doi: 10.1016/0165-1161(81)90026-1.
We show from simple theory that the number of mutants observed in the Ames assay should be approximately proportional to alpha Cn0P where alpha is the mutation rate per concentration of mutagen, C; n0 is the initial inoculum; and P is the average number of bacteria per colony in the background lawn. We tested this theory by carrying out Ames assays for the directly acting mutagen 2-nitrofulorene on TA98 as a function of initial inoculum over the range 10(4)-10(8) bacteria/plate. P was assumed to be proportional to the average volume of the background colonies and was estimated from 100X photomicrographs of the background lawn. The initial inoculum was determined by counting background colonies in the photomicrography, by dilution-plating, and by electronic particle counting. We found that the number of mutants depended weakly on n0, but the dependence could be quantitatively accounted for by the simple theory. These data and the theory explain the least some of the reported variations in quantitation of the Ames assay; show that the slopes of dose response curves depend on n0; explain the range observed for spontaneous revertants; suggest some limitations to quantifying the Ames assay and, within these limits, suggest a method for normalizing independently obtained Ames assay data.
我们从简单理论表明，在艾姆斯试验中观察到的突变体数量应大致与αCn0P成正比，其中α是每单位诱变剂浓度（C）的突变率；n0是初始接种量；P是背景菌苔中每个菌落的平均细菌数。我们通过对直接作用的诱变剂2-硝基芴在TA98菌株上进行艾姆斯试验来检验这一理论，试验中初始接种量在10⁴ - 10⁸个细菌/平板范围内变化。假设P与背景菌落的平均体积成正比，并通过对背景菌苔的100倍显微照片进行估算。初始接种量通过在显微照片中计数背景菌落、稀释平板法以及电子粒子计数来确定。我们发现突变体数量对n0的依赖性较弱，但这种依赖性可以用该简单理论进行定量解释。这些数据和理论至少解释了一些报道的艾姆斯试验定量中的差异；表明剂量反应曲线的斜率取决于n0；解释了自发回复突变体观察到的范围；指出了量化艾姆斯试验的一些局限性，并在这些局限范围内提出了一种对独立获得的艾姆斯试验数据进行标准化的方法。
