Distribution of fitness effects caused by random insertion mutations in Escherichia coli
Distribution of fitness effects caused by random insertion mutations in Escherichia coli
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DOI：
10.1023/a:1017031008316
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发表时间：
1998-01-01
期刊：
影响因子：
1.5
通讯作者：
Lenski, RE
中科院分区：
文献类型：
--
作者：
Elena, SF;Ekunwe, L;Lenski, RE
关于突变对生物体适应性的影响的分布，人们知之甚少，尽管这些信息对于进化研究具有根本的重要性。这种信息的缺乏反映了这样一个事实，即通常难以仅使用等位基因频率的静态分布来量化突变和自然选择的动态影响。在这项研究中，我们采取了直接的方法来测量突变对适应性的影响。我们使用转座子诱变，以创建226突变克隆的大肠杆菌。每个突变克隆携带Tn10衍生物的单个随机插入。所有226个突变体都独立地来自同一个祖先克隆，该祖先克隆是从在恒定的实验室环境中进化了10，000代的群体中获得的。然后，我们进行了竞争实验，以衡量每个突变对健身相对于一个共同的竞争对手的影响。至少80%的突变对适应性有显著的负面影响，而没有一个突变有显著的正面影响。平均而言，突变使适应度降低了约3%，但适应度效应的分布高度偏斜，并且具有长而平的尾部。一个复合分布，其中包括伽玛和均匀的组件，提供了一个很好的适合观察到的健身值。
Very little is known about the distribution of mutational effects on organismal fitness, despite the fundamental importance of this information for the study of evolution. This lack of information reflects the fact that it is generally difficult to quantify the dynamic effects of mutation and natural selection using only static distributions of allele frequencies. In this study, we took a direct approach to measuring the effects of mutations on fitness. We used transposon-mutagenesis to create 226 mutant clones of Escherichia coli. Each mutant clone carried a single random insertion of a derivative of Tn10. All 226 mutants were independently derived from the same progenitor clone, which was obtained from a population that had evolved in a constant laboratory environment for 10,000 generations. We then performed competition experiments to measure the effect of each mutation on fitness relative to a common competitor. At least 80% of the mutations had a significant negative effect on fitness, whereas none of the mutations had a significant positive effect. The mutations reduced fitness by about 3%, on average, but the distribution of fitness effects was highly skewed and had a long, flat tail. A compound distribution, which includes both gamma and uniform components, provided an excellent fit to the observed fitness values.