The ability to sequence genes and, more recently, whole genomes has transformed our understanding of the tree of life by elucidating the tremendous diversity of microorganisms and by placing plants, animals, and fungi as branches nested among microbial lineages (1–3). The resulting evolutionary tree divides life into three domains: the exclusively microbial Bacteria and Archaea, and Eukarya, organisms whose cells contain nuclei (including ciliates, amoebae, and animals). Yet, the ordering of the earliest branching events on the tree and the nature of now-extinct ancestors remains unclear. On page 588 of this issue, Coleman et al. (4) provide a new estimate of the root of the bacterial tree of life, that is, the ancestor from which all bacterial species are derived. Knowledge of the root of the bacterial tree is important because it defines the evolutionary starting point for the tremendous diversity of Bacteria and offers glimpses into the nature of the first bacterial cells.
Katz, Laura A., "Illuminating the First Bacteria" (2021). Biological Sciences: Faculty Publications, Smith College, Northampton, MA.
Peer reviewed accepted manuscript.