Abstract: 

Oxygenic phototrophs have played a fundamental role in Earth’s history by enabling the rise of atmospheric oxygen (O₂) and paving the way for complex life.  Their origin fundamentally transformed the biology and geochemistry of our planet. During my talk, I will highlight some of the key events in the evolutionary history of Cyanobacteria: the Archean origin of PSII (the photochemical reaction center that catalyzes the light-driven oxidation of water to molecular oxygen), the origin of the crown group of Cyanobacteria, the emergence of filamentous forms around the Great Oxidation Event (2.32 Ga), and the late emergence of marine planktonic groups between 800-600 Mya.  Molecular evolution analyses overall show that there is a huge lag between the Archean origin of oxygenic photosynthesis and planktonic forms at the end of the Precambrian. By studying the ‘genomic record’ we can now unravel how oxygenic phototrophs co-evolved with the Earth’s biosphere, thereby making our planet habitable.