The extreme geological environments, such as marine oxygen minimum zones, methane cold seeps, hydrothermal vents, coastal hypoxic zones, and acid mine drainages, are extensively studied by a wide range of geoscientists and geobiologists. The exceptionally high concentrations of methane, hydrogen sulfide, and/or very low pH in these environments significantly influence microbiological processes and the biogeochemical cycles of C, S, Fe, and various trace elements, including U and Mo. Diverse S-related and Fe-related microbial metabolisms are associated with CO2-fixation and organic carbon remineralization or sequestration, acting as key drivers of the planetary redox state and climate over geological timescales. We welcome contributions that document modern environmental chemistry, geobiology, geochemistry, geomicrobiological experiments, and modeling or models that enhance our understanding of the coupled C-S-Fe and trace metal cycles from the present to deep time.