Lawrence J G, Ochman H, Hartl D L
Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110.
J Gen Microbiol. 1991 Aug;137(8):1911-21. doi: 10.1099/00221287-137-8-1911.
Classification of bacterial species into genera has traditionally relied upon variation in phenotypic characteristics. However, these phenotypes often have a multifactorial genetic basis, making unambiguous taxonomic placement of new species difficult. By designing evolutionarily conserved oligonucleotide primers, it is possible to amplify homologous regions of genes in diverse taxa using the polymerase chain reaction and determine their nucleotide sequences. We have constructed a phylogeny of some enteric bacteria, including five species classified as members of the genus Escherichia, based on nucleotide sequence variation at the loci encoding glyceraldehyde-3-phosphate dehydrogenase and outer membrane protein 3A, and compared this genealogy with the relationships inferred by biotyping. The DNA sequences of these genes defined congruent and robust phylogenetic trees indicating that they are an accurate reflection of the evolutionary history of the bacterial species. The five species of Escherichia were found to be distantly related and, contrary to their placement in the same genus, do not form a monophyletic group. These data provide a framework which allows the relationships of additional species of enteric bacteria to be inferred. These procedures have general applicability for analysis of the classification, evolution, and epidemiology of bacterial taxa.
传统上，细菌物种的属分类依赖于表型特征的差异。然而，这些表型往往具有多因素的遗传基础，使得新物种的明确分类定位变得困难。通过设计进化保守的寡核苷酸引物，利用聚合酶链反应扩增不同分类群中基因的同源区域并确定其核苷酸序列成为可能。我们基于编码甘油醛-3-磷酸脱氢酶和外膜蛋白3A的基因座处的核苷酸序列变异，构建了包括五种被归类为大肠杆菌属成员的肠道细菌的系统发育树，并将该谱系与生物分型推断的关系进行了比较。这些基因的DNA序列定义了一致且稳健的系统发育树，表明它们准确反映了细菌物种的进化历史。发现这五种大肠杆菌亲缘关系较远，与它们被置于同一属的情况相反，它们并未形成一个单系群。这些数据提供了一个框架，可据此推断其他肠道细菌物种之间的关系。这些方法对于分析细菌分类群的分类、进化和流行病学具有普遍适用性。
