Microbial Life Tree

A COMPLEX TREE OF LIFE—Microbes are living archives of Earth’s evolutionary history. The discovery of a great variety of deep-sea microorganisms (using diverse metabolic strategies to live in diverse habitats) indicates that they evolved along different evolutionary pathways. Using genetic analyses, scientists can trace these pathways to reconstruct when various microbial biochemical and metabolic machinery developed, diverged, or intermingled in the three major domains of life: bacteria, archaea, and eukaryotes. (Illustration by Jayne Doucette, © Woods Hole Oceanographic Institution)