Nikolich M P, Hong G, Shoemaker N B, Salyers A A
Department of Microbiology, University of Illinois, Urbana 61801.
Appl Environ Microbiol. 1994 Sep;60(9):3255-60. doi: 10.1128/aem.60.9.3255-3260.1994.
Though numerous studies have shown that gene transfer occurs between distantly related bacterial genera under laboratory conditions, the frequency and breadth of horizontal transfer events in nature remain unknown. Previous evidence for natural intergeneric transfers came from studies of genes in human pathogens, bacteria that colonize the same host. We present evidence that natural transfer of a tetracycline resistance gene, tetQ, has occurred between bacterial genera that normally colonize different hosts. A DNA sequence comparative approach was taken to examine the extent of horizontal tetQ dissemination between species of Bacteroides, the predominant genus of the human colonic microflora, and between species of Bacteroides and of the distantly related genus Prevotella, a predominant genus of the microflora of the rumens and intestinal tracts of farm animals. Virtually identical tetQ sequences were found in a number of isolate pairs differing in taxonomy and geographic origin, indicating that extensive natural gene transmission has occurred. Among the exchange events indicated by the evidence was the very recent transfer of an allele of tetQ usually found in Prevotella spp. to a Bacteroides fragilis strain.
尽管众多研究表明，在实验室条件下，基因转移会发生在亲缘关系较远的细菌属之间，但自然环境中水平转移事件的频率和广度仍不清楚。此前关于自然属间转移的证据来自对人类病原体（即定殖于同一宿主的细菌）中基因的研究。我们提供的证据表明，四环素抗性基因tetQ在通常定殖于不同宿主的细菌属之间发生了自然转移。我们采用了DNA序列比较方法，来检测tetQ在拟杆菌属（人类结肠微生物群的主要菌属）的不同物种之间，以及拟杆菌属与亲缘关系较远的普雷沃氏菌属（农场动物瘤胃和肠道微生物群的主要菌属）的不同物种之间的水平传播程度。在许多分类学和地理来源不同的分离株对中，发现了几乎相同的tetQ序列，这表明已经发生了广泛的自然基因传递。证据显示的交换事件中，包括一个通常在普雷沃氏菌属中发现的tetQ等位基因最近转移到了一株脆弱拟杆菌中。
