Major New Microbial Groups Expand Diversity and Alter Our Understanding of the Tree of Life

The recent recovery of genomes for organisms from phyla with no isolated representative (candidate phyla) via cultivation-independent genomics enabled delineation of major new microbial lineages, namely the bacterial candidate phyla radiation (CPR), DPANN archaea, and Asgard archaea. CPR and DPANN organisms are inferred to be mostly symbionts, and some are episymbionts of other microbial community members. Asgard genomes encode typically eukaryotic systems, and their inclusion in phylogenetic analyses results in placement of eukaryotes as a branch within Archaea. Here, we illustrate how new genomes have changed the structure of the tree of life and altered our understanding of biology, evolution, and metabolic roles in biogeochemical processes.