How did life come to tolerate and thrive in an oxygenated world?

Looking across our planet's four-and-a-half billion-year history, the rise of dioxygen-an interval sometimes called the Great Oxygenation Event (GOE)-is arguably the most important environmental change. This revolution occurred approximately 2.3 billion years ago, roughly at the mid-way point in Earth history, and it was ultimately driven by a biological innovation: the evolution of oxygenic photosynthesis. The evolution of oxygenic photosynthesis conferred the ability to use water as a photosynthetic substrate (earlier photosynthesis was anoxygenic and required reduced iron, sulfur, carbon, or hydrogen). Primary productivity-no longer limited by a source of electrons-greatly expanded across the Earth surface. In turn, dioxygen accumulated and became widely available for use in anabolic and catabolic metabolisms, forming a rich cascade of evolutionary potential and consequence. The modern biosphere figured out how to balance harmful oxidative stress with the beneficial ways dioxygen can be used. But how did life come to first tolerate and then thrive in an oxygenated world? It's this question that attracted the diverse perspectives reflected in this special issue.