Department of Biochemistry and Biomedical Sciences, McMaster University Hamilton, ON, Canada.
Front Microbiol. 2013 Jul 30;4:217. doi: 10.3389/fmicb.2013.00217. eCollection 2013.
The Spirochaetes species cause many important diseases including syphilis and Lyme disease. Except for their containing a distinctive endoflagella, no other molecular or biochemical characteristics are presently known that are specific for either all Spirochaetes or its different families. We report detailed comparative and phylogenomic analyses of protein sequences from Spirochaetes genomes to understand their evolutionary relationships and to identify molecular signatures for this group. These studies have identified 38 conserved signature indels (CSIs) that are specific for either all members of the phylum Spirochaetes or its different main clades. Of these CSIs, a 3 aa insert in the FlgC protein is uniquely shared by all sequenced Spirochaetes providing a molecular marker for this phylum. Seven, six, and five CSIs in different proteins are specific for members of the families Spirochaetaceae, Brachyspiraceae, and Leptospiraceae, respectively. Of the 19 other identified CSIs, 3 are uniquely shared by members of the genera Sphaerochaeta, Spirochaeta, and Treponema, whereas 16 others are specific for the genus Borrelia. A monophyletic grouping of the genera Sphaerochaeta, Spirochaeta, and Treponema distinct from the genus Borrelia is also strongly supported by phylogenetic trees based upon concatenated sequences of 22 conserved proteins. The molecular markers described here provide novel and more definitive means for identification and demarcation of different main groups of Spirochaetes. To accommodate the extensive genetic diversity of the Spirochaetes as revealed by different CSIs and phylogenetic analyses, it is proposed that the four families of this phylum should be elevated to the order level taxonomic ranks (viz. Spirochaetales, Brevinematales ord. nov., Brachyspiriales ord. nov., and Leptospiriales ord. nov.). It is further proposed that the genera Borrelia and Cristispira be transferred to a new family Borreliaceae fam. nov. within the order Spirochaetales.
螺旋体属引起许多重要疾病，包括梅毒和莱姆病。除了它们含有独特的端鞭毛外，目前还不知道其他分子或生化特征是所有螺旋体或其不同科特有的。我们报告了螺旋体属基因组蛋白序列的详细比较和系统基因组分析，以了解它们的进化关系，并确定该组的分子特征。这些研究确定了 38 个保守特征缺失（CSIs），这些缺失要么是所有螺旋体门成员特有的，要么是其不同主要分支特有的。在这些 CSIs 中，FlgC 蛋白中的 3 个氨基酸插入物是所有测序螺旋体所共有的，为该门提供了一个分子标记。不同蛋白质中的 7、6 和 5 个 CSI 分别是螺旋体科、短螺旋体科和钩端螺旋体科成员特有的。在其他 19 个确定的 CSIs 中，有 3 个是 Sphaerochaeta、Spirochaeta 和 Treponema 属成员所共有的，而其他 16 个是 Borrelia 属特有的。基于 22 个保守蛋白的串联序列构建的系统发育树也强烈支持 Sphaerochaeta、Spirochaeta 和 Treponema 属的单系分组，与 Borrelia 属明显不同。这里描述的分子标记为不同主要螺旋体群的鉴定和划分提供了新颖和更明确的手段。为了适应不同 CSIs 和系统发育分析揭示的螺旋体的广泛遗传多样性，建议将该门的四个科提升到分类等级（即螺旋体目、Brevinematales 目、Brachyspiriales 目和 Leptospiriales 目）。进一步建议将 Borrelia 和 Cristispira 属转移到螺旋体目内的一个新科 Borreliaceae fam。nov.。
