School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, UK.
Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
Science. 2021 May 7;372(6542). doi: 10.1126/science.abe0511.
A rooted bacterial tree is necessary to understand early evolution, but the position of the root is contested. Here, we model the evolution of 11,272 gene families to identify the root, extent of horizontal gene transfer (HGT), and the nature of the last bacterial common ancestor (LBCA). Our analyses root the tree between the major clades Terrabacteria and Gracilicutes and suggest that LBCA was a free-living flagellated, rod-shaped double-membraned organism. Contrary to recent proposals, our analyses reject a basal placement of the Candidate Phyla Radiation, which instead branches sister to Chloroflexota within Terrabacteria. While most gene families (92%) have evidence of HGT, overall, two-thirds of gene transmissions have been vertical, suggesting that a rooted tree provides a meaningful frame of reference for interpreting bacterial evolution.
为了理解早期进化，一个有根的细菌树是必要的，但根的位置存在争议。在这里，我们对 11272 个基因家族的进化进行建模，以确定根、水平基因转移（HGT）的程度以及细菌最后共同祖先（LBCA）的性质。我们的分析将树定位于主要菌群 Terrabacteria 和 Gracilicutes 之间，并表明 LBCA 是一种自由生活的、有鞭毛的、杆状的双层膜生物。与最近的提议相反，我们的分析拒绝了候选门辐射的基础位置，而是在 Terrabacteria 中与 Chloroflexota 分支姐妹。虽然大多数基因家族（92%）有 HGT 的证据，但总体而言，三分之二的基因传递是垂直的，这表明有根的树为解释细菌进化提供了一个有意义的参考框架。
