How manganese empowered life with dioxygen (and vice versa)

Throughout the history of life on Earth, abiotic components of the environment have shaped the evolution of life, and in turn life has shaped the environment. The element manganese embodies a special aspect of this collaboration; its history is closely entwined with those of photosynthesis and O2—two reigning features that characterize the biosphere today. Manganese chemistry was central to the environmental context and evolutionary innovations that enabled the origin of oxygenic photosynthesis and the ensuing rise of O2. It was also manganese chemistry that provided an early, fortuitous antioxidant system that was instrumental in how life came to cope with oxidative stress and ultimately thrive in an aerobic world. Subsequently, the presence of O2 transformed the biogeochemical dynamics of the manganese cycle, enabling a rich suite of environmental and biological processes involving high-valent manganese and manganese redox cycling. Here, we describe insights from chemistry, biology, and geology, to examine manganese dynamics in the environment, and its unique role in the history of life.