Bacterial microcompartments (BMCs) are self-assembling prokaryotic organelles which encapsulate enzymes within a polyhedral protein shell. The shells are comprised of only two structural modules, distinct domains that form pentagonal and hexagonal building blocks, which occupy the vertices and facets, respectively. As all BMC loci encode at least one hexamer-forming and one pentamer-forming protein, the evolutionary history of BMCs can be interrogated from the perspective of their shells. Here, we discuss how structures of intact shells and detailed phylogenies of their building blocks from a recent phylogenomic survey distinguish families of these domains and reveal clade-specific structural features. These features suggest distinct functional roles that recur across diverse BMCs. For example, it is clear that carboxysomes independently arose twice from metabolosomes, yet the principles of shell assembly are remarkably conserved.

细菌微区室 (BMC) 是自组装原核细胞器，将酶封装在多面体蛋白壳内。壳仅由两个结构模块组成，即形成五边形和六边形构建块的不同域，分别占据顶点和面。由于所有 BMC 位点都编码至少一种六聚体形成蛋白和一种五聚体形成蛋白，因此可以从 BMC 外壳的角度来探究 BMC 的进化史。在这里，我们讨论了最近的系统发育组调查中完整壳的结构和其构件的详细系统发育如何区分这些域的家族并揭示进化枝特定的结构特征。这些特征表明不同 BMC 中重复出现的不同功能角色。例如，很明显，羧基体独立地从代谢体中产生两次，但壳组装的原理却非常保守。