Fitness effects of advantageous mutations in evolving Escherichia coli populations
Fitness effects of advantageous mutations in evolving Escherichia coli populations
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DOI：
10.1073/pnas.98.3.1113
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发表时间：
2001-01-30
影响因子：
11.1
通讯作者：
Schlötterer, C
中科院分区：
文献类型：
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作者：
Imhof, M;Schlötterer, C
在自然种群中，有益突变在适应过程中的核心作用已经确立。因此，研究有益突变的性质一直是一个长期的兴趣。然而，它们的行频率使得这类突变几乎无法进行系统研究。在缺乏实验数据的情况下，假定有益突变的适应性效应的分布类似于有害突变的分布。对于这一假设的实验证明，我们使用了一种新的标记系统，以跟踪适应性事件在不断发展的大肠杆菌培养，并确定这些有益的突变的选择性优势。10个平行培养物通过连续转移繁殖约1，000代，并鉴定出66个适应性事件。根据这个数据集，我们估计每个细胞和世代的有益突变率为4 × 10（-9）。与适应度效应的指数分布一致，我们观察到大部分有利突变具有小效应，只有少数具有大效应。在我们的实验中，有利突变的平均选择系数为0.02。
The central role of beneficial mutations for adaptive processes in natural populations is well established. Thus, there has been a long-standing interest to study the nature of beneficial mutations. Their row frequency, however, has made this class of mutations almost inaccessible for systematic studies. in the absence of experimental data, the distribution of the fitness effects of beneficial mutations was assumed to resemble that of deleterious mutations. For an experimental proof of this assumption, we used a novel marker system to trace adaptive events in an evolving Escherichia coli culture and to determine the selective advantage of those beneficial mutations. Ten parallel cultures were propagated for about 1,000 generations by serial transfer, and 66 adaptive events were identified. From this data set, we estimate the rate of beneficial mutations to be 4 x 10(-9) per cell and generation. Consistent with an exponential distribution of the fitness effects, we observed a large fraction of advantageous mutations with a small effect and only few with large effect, The mean selection coefficient of advantageous mutations in our experiment was 0.02.