Deep mitochondrial origin outside the sampled alphaproteobacteria

Mitochondria are ATP-generating organelles whose endosymbiotic origin has been a key event in the evolution of eukaryotic cells. Despite overwhelming phylogenetic evidence for an alphaproteobacterial ancestry, efforts to pinpoint the closest relatives among the sampled alphaproteobacteria have been conflicting, complicating detailed inferences about the identity and nature of the mitochondrial ancestor. While most studies support that mitochondria evolved from an ancestor related to Rickettsiales, an order that includes several host-associated pathogenic and endosymbiotic lineages, others suggest that mitochondria evolved from a free-living group. Here we re-evaluate the phylogenetic placement of mitochondria. We employ genome-resolved binning of oceanic metagenome datasets and increase the genomic sampling of Alphaproteobacteria with twelve novel divergent clades, and one novel clade representing a sister group to all Alphaproteobacteria. Subsequent phylogenomic analyses that specifica...线粒体是生成三磷酸腺苷（ATP）的细胞器，其内共生起源事件是真核细胞演化历程中的关键节点。尽管已有大量系统发育学证据支持线粒体起源于α-变形菌门（Alphaproteobacteria），但学界在确定已采样α-变形菌门类群中与线粒体亲缘关系最近类群的相关研究中始终存在分歧，这使得针对线粒体祖先的身份与本质的精细推断变得更为复杂。多数研究认为线粒体起源于与立克次体目（Rickettsiales）亲缘关系较近的祖先——该类群包含多种宿主相关的致病及内共生谱系——但也有研究提出线粒体起源于自由生活的类群。本研究重新评估了线粒体的系统发育定位：我们通过对海洋宏基因组数据集开展基因组解析分箱，新增了12个全新的分歧演化支以及1个作为所有α-变形菌门姊妹群的全新演化支，从而扩大了α-变形菌门的基因组采样范围。后续进行的系统发育基因组学分析，其相关内容原文此处截断