Novel spp. from Diverse Environments across the Globe.

Photosynthetic and their descendants are the only known organisms capable of oxygenic photosynthesis. Their metabolism permanently changed the Earth's surface and the evolutionary trajectory of life, but little is known about their evolutionary history. Genomes of the , an order of deeply divergent photosynthetic , may hold clues about the evolutionary process. However, there are only three published genomes within this order, and it is difficult to make broad inferences based on such little data. Here, I describe five species within the retrieved from publicly available databases and examine their photosynthetic gene content and the environments in which genomes and 16S rRNA gene sequences are found. The contain reduced photosystems and inhabit cold, wet-rock, and low-light environments. They are likely present in low abundances due to their low growth rate. Future searches for should target these environments, and samples should be deeply sequenced to capture the low-abundance taxa. Publicly available databases contain undescribed taxa within the . However, searching through all available data with current methods is computationally expensive. Therefore, new methods must be developed to search for these and other evolutionarily important taxa. Once identified, these novel photosynthetic will help illuminate the origin and evolution of oxygenic photosynthesis. Early branching photosynthetic such as the may provide clues into the evolutionary history of oxygenic photosynthesis, but there are few genomes or cultured taxa from this order. Five new metagenome-assembled genomes suggest that members of the all contain reduced photosystems and lack genes associated with thylakoids and circadian rhythms. Their distribution suggests that they may thrive in environments that are marginal for other species, including wet-rock and cold environments. These traits may aid in the discovery and cultivation of novel species in this clade.