Reconstructing Early Microbial Life.

For more than 3.5 billion years, life experienced dramatic environmental extremes on Earth. These include shifts from oxygen-less to overoxygenated atmospheres and cycling between hothouse conditions and global glaciations. Meanwhile, an ecological revolution took place. Earth evolved from one dominated by microbial life to one containing the plants and animals that are most familiar today. Many key cellular features evolved early in the history of life, collectively defining the nature of our biosphere and underpinning human survival. Recent advances in molecular biology and bioinformatics have greatly improved our understanding of microbial evolution across deep time. However, the incorporation of molecular genetics, population biology, and evolutionary biology approaches into the study of Precambrian biota remains a significant challenge. This review synthesizes our current knowledge of early microbial life with an emphasis on ancient metabolisms. It also outlines the foundations of an emerging interdisciplinary area that integrates microbiology, paleobiology, and evolutionary synthetic biology to reconstruct ancient biological innovations.