Cyanobacteria and biogeochemical cycles through Earth history

Cyanobacteria are the only prokaryotes to have evolved oxygenic photosynthesis, transforming the biology and chemistry of our planet. Genomic and evolutionary studies have revolutionized our understanding of early oxygenic phototrophs, complementing and dramatically extending inferences from the geologic record. Molecular clock estimates point to a Paleoarchean origin (3.6–3.2 billion years ago, bya) of the core proteins of Photosystem II (PSII) involved in oxygenic photosynthesis and a Mesoarchean origin (3.2–2.8 bya) for the last common ancestor of modern cyanobacteria. Nonetheless, most extant cyanobacteria diversified after the Great Oxidation Event (GOE), an environmental watershed ca. 2.45 bya made possible by oxygenic photosynthesis. Throughout their evolutionary history, cyanobacteria have played a key role in the global carbon cycle. The core proteins of PSII involved in oxygenic photosynthesis originated during the early Archean, well before the GOE occurring around 2.3 billion years ago.Most extant cyanobacterial taxa, including the lineage leading to chloroplasts, diversified after the GOE.The evolution of modern planktonic cyanobacteria and phytoplanktonic algae reached global prominence at the end of the Precambrian, and they continue to significantly contribute to the carbon cycle.Prior to the origin of complex life, cyanobacteria were the main primary producers during most of the Proterozoic Eon.