Geomicrobiology of Iron in Extreme Environments

The rapid redox cycling of iron is one of the most pervasive geochemical processes catalyzed by microbial organisms. Numerous microbial metabolisms rely on transferring electrons to and from iron, even in “extreme” environments considered challenging for life due to high acidity, high alkalinity, high temperature, low organic content, or low water abundance. Recent efforts to explore the iron biogeochemistry of extreme systems, such as hydrothermal vents, seafloor basalts, serpentinizing systems, and acid mine drainage, have significantly expanded our expectations regarding the distribution and activity of iron-dependent life on Earth, and potentially other iron-rich silicate planets, such as Mars.