Whittam T S, Ochman H, Selander R K
Proc Natl Acad Sci U S A. 1983 Mar;80(6):1751-5. doi: 10.1073/pnas.80.6.1751.
A survey of allozyme variation at 12 enzyme loci in 1,705 clones of the genetic species Escherichia coli (including four species of Shigella) from natural populations revealed 302 unique allele combinations (electrophoretic types). Single-locus diversity estimates fall within the range predicted by the neutral allele theory of molecular evolution, but the combination of alleles in electrophoretic types are highly nonrandom, as indicated by a test of association over all loci and by evidence of complex linkage disequilibria in several four-locus combinations. These linkage disequilibria reflect genetic differentiation of E. coli into three groups of strains. Because of restricted recombination, both the stochastic extinction of lines and selective differences between particular genetic combinations may have contributed to the evolution of subspecific structure in E. coli.
对来自自然种群的1705个大肠杆菌遗传种（包括四种志贺氏菌）克隆的12个酶位点的等位酶变异进行的一项调查揭示了302种独特的等位基因组合（电泳类型）。单基因座多样性估计值落在分子进化中性等位基因理论预测的范围内，但电泳类型中等位基因的组合是高度非随机的，这通过对所有基因座的关联测试以及几个四基因座组合中复杂连锁不平衡的证据得以表明。这些连锁不平衡反映了大肠杆菌分化为三组菌株的遗传差异。由于重组受限，品系的随机灭绝和特定遗传组合之间的选择性差异都可能促成了大肠杆菌亚种结构的进化。
