Planetary microbiology: microbes, planets, and the search for life

ABSTRACT Life on Earth has been shaped by transformative microbial innovations and singularities that redefined planetary systems, from oxygenic photosynthesis to biological nitrogen fixation. These unique events, occurring only once in life’s tractable history, laid the foundation for the complex ecosystems and global biogeochemical cycles around us today. The Planetary Microbiology collection in Applied and Environmental Microbiology explores how modern microbiological tools reveal the origins, early evolution, and planetary impacts of these microbial breakthroughs. Spanning deep-time studies, extreme environments, and astrobiology, contributions in this issue link biosignatures and ancient microbes to the search for extraterrestrial life. By bridging molecular, ecological, and planetary scales, planetary microbiology illuminates life’s past while critically informing strategies for the environmental and exploration challenges of our future.