Abstract
Electroautotrophy-the use of extracellular electrons as the primary energy source for autotrophic metabolism-remains understudied compared to photoautotrophy and chemoautotrophy. Its occurrence in deep-earth and deep-sea environments suggests profound implications for astrobiology, yet electroautotrophic microorganisms remain poorly explored. This review synthesizes the discovery of electroautotrophs and current knowledge from laboratory and field studies, including insights from the deep biosphere. We evaluate their ecological roles on Earth and discuss their potential significance in possible life-supporting ecosystems elsewhere and in life-detection strategies. Finally, we propose six key research priorities to advance the study of electroautotrophy in astrobiological contexts.