Waterhouse Janet C, Russell Roy R B
Oral Biology, School of Dental Sciences, University of Newcastle, Newcastle upon Tyne NE2 4BW, UK.
Microbiology (Reading). 2006 Jun;152(Pt 6):1777-1788. doi: 10.1099/mic.0.28647-0.
A range of properties, including the ability to utilize various sugars, bind macromolecules and produce mutacins, are known to vary in their occurrence in different strains of Streptococcus mutans. In addition, insertion-sequence elements show a limited distribution and sequencing of the genome of S. mutans UA159 has revealed the presence of putative genomic islands of atypical base composition indicative of foreign DNA. PCR primers flanking regions suspected of having inserted DNA were designed on the basis of the genome sequence of S. mutans UA159 and used to explore variation in a collection of 39 strains isolated in various parts of the world over the last 40 years. Extensive differences between strains were detected, and similar insertion/deletion events appear to be present in the genomes of strains with very different origins. In two instances, insertion of foreign DNA appears to have displaced original S. mutans genes. Together with previous results on the occurrence of deletions in genes associated with sugar metabolism, the results indicate that S. mutans has a core genome and a dispensable genome, and that dispensable genes have become widely distributed through horizontal transfer.
一系列特性，包括利用各种糖类的能力、结合大分子的能力以及产生变链菌素的能力，在不同变形链球菌菌株中的出现情况各不相同。此外，插入序列元件分布有限，对变形链球菌UA159基因组的测序揭示了存在非典型碱基组成的假定基因组岛，这表明存在外源DNA。根据变形链球菌UA159的基因组序列设计了侧翼为疑似插入DNA区域的PCR引物，并用于探究在过去40年中从世界各地分离出的39株菌株中的变异情况。检测到菌株之间存在广泛差异，并且在起源非常不同的菌株基因组中似乎存在相似的插入/缺失事件。在两个实例中，外源DNA的插入似乎取代了原始的变形链球菌基因。连同先前关于与糖代谢相关基因中缺失情况的结果，这些结果表明变形链球菌具有核心基因组和可 dispensable 基因组，并且可 dispensable 基因已通过水平转移广泛分布。 （注：原文中“dispensable”未翻译，因为不确定其准确含义，需结合更多背景信息确定合适译名）
