Synonymous genetic variation in natural isolates of Escherichia coli does not predict where synonymous substitutions occur in a long-term experiment

Synonymous genetic differences vary by more than 20-fold among genes in natural isolates of Escherichia coli. One hypothesis to explain this heterogeneity is that genes with high levels of synonymous variation mutate at higher rates than genes with low synonymous variation. If so, then one would expect to observe similar mutational patterns in evolution experiments. In fact, however, the pattern of synonymous substitutions in a long-term evolution experiment with E. coli does not support this hypothesis. In particular, the extent of synonymous variation across genes in that experiment does not reflect the variation observed in natural isolates of E. coli. Instead, gene length alone predicts with high accuracy the prevalence of synonymous changes in the experimental populations. We hypothesize that patterns of synonymous variation in natural E. coli populations are instead caused by differences across genomic regions in their effective population size that, in turn, reflect different his...

在大肠杆菌（Escherichia coli）的自然分离株中，不同基因间的同义遗传差异幅度可达20倍以上。为解释这一异质性，有假说提出：同义变异水平较高的基因，其突变率高于同义变异水平较低的基因。若该假说成立，则在进化实验中应能观测到相似的突变模式。然而事实上，一项基于大肠杆菌的长期进化实验中观测到的同义替换模式，并不支持这一假说。具体而言，该实验中不同基因的同义变异程度，无法反映大肠杆菌自然分离株中观测到的变异情况。与之相反，仅通过基因长度即可高精度预测实验种群中同义替换的发生频率。我们提出另一假说：大肠杆菌自然种群的同义变异模式，实则由基因组不同区域的有效种群大小差异所导致，而后者又反映了不同的[原文未完结]