DISTRIBUTION OF GLOEOBACTERALES AND VAMPIROVIBRIONIA AND THE POTENTIAL HABITATS INHABITED BY THE EARLIEST CYANOBACTERIIA

The evolution of oxygenic photosynthesis in the Cyanobacteria was one of the most transformative events in Earth history, eventually leading to the oxygenation of Earth’s atmosphere. However, it is difficult to constrain when photosynthesis evolved in part because we do not understand the ecology of the earliest phototrophs including the environments in which they lived. Here, we use a cutting-edge bioinformatics tool to survey nearly 500,000 metagenomes for relatives of the Gloeobacteria and the Vampirovibronia, the taxa that likely bookended the evolution of oxygenic photosynthesis to identify the modern environments in which these organisms live. Ancestral state reconstruction suggests that the common ancestors of these organisms lived in freshwater environments. This restricted distribution may have increased the lag between the evolution of oxygenic photosynthesis and the oxygenation of Earth’s atmosphere.