Abstract：
The order Rickettsiales (Alphaproteobacteria) encompasses multiple diverse lineages of host-associated bacteria, including pathogens, reproductive manipulators, and mutualists. Here, in order to understand how intracellularity and host association originated in this order, and whether they are ancestral or convergently evolved characteristics, we built a large and phylogenetically-balanced dataset that includes de novo sequenced genomes and a selection of published genomic and metagenomic assemblies. We perform detailed functional reconstructions that clearly indicates \"late\" and parallel evolution of obligate host-association in different Rickettsiales lineages. According to the depicted scenario, multiple independent horizontal acquisitions of transporters led to the progressive loss of biosynthesis of nucleotides, amino acids and other metabolites, producing distinct conditions of host-dependence. Each clade experienced a different pattern of evolution of the ancestral arsenal of interaction apparatuses, including development of specialised effectors involved in the lineage-specific mechanisms of host cell adhesion and/or invasion.
摘要：
Rickettsiales（α变形杆菌）包括宿主相关细菌的多个不同谱系，包括病原体,生殖操纵者，和互惠主义者。这里,为了理解细胞内和宿主关联是如何起源于这个顺序的，无论它们是祖先还是收敛进化的特征，我们建立了一个大型且系统发育平衡的数据集，其中包括从头测序的基因组以及已发表的基因组和宏基因组组件的选择。我们进行了详细的功能重建，清楚地表明了不同Rickettsiales谱系中专性宿主关联的“晚期”和平行进化。根据描述的场景，转运蛋白的多个独立水平收购导致核苷酸生物合成的逐步丧失，氨基酸和其他代谢物，产生不同的宿主依赖条件。每个进化枝都经历了相互作用装置祖先武器库的不同演变模式，包括参与宿主细胞粘附和/或侵袭的谱系特异性机制的专门效应子的开发。
