The subsurface hosts a biosphere in which microbial activities are tightly coupled to geological and biogeochemical processes. Across aquifers, sediments, and deep continental and oceanic crust, microorganisms obtain energy and nutrients from minerals, fluids, gases, and organic matter while transforming minerals, fluid chemistry, and elemental fluxes. Fundamental questions remain about how microorganisms persist under severe energy limitation, how geological and hydrological conditions regulate microbial ecophysiology and metabolism, and when microbial activity becomes significant for subsurface biogeochemical cycling.
This session explores reciprocal interactions between subsurface microorganisms and their geological environments. We welcome studies examining how mineralogy, fluid chemistry, redox conditions, hydrological connectivity, and energy availability shape microbial diversity, community assembly, activity, and metabolism, as well as how microorganisms drive mineral dissolution and precipitation, redox transformations, and mineral-mediated electron transfer.
Key topics include microbial survival under energy and nutrient limitation and physicochemical extremes; utilization of mineral-associated nutrients and geologically derived electron donors and acceptors; extracellular electron transfer; coupled carbon, nitrogen, sulfur, iron, methane, hydrogen, and other elemental cycles; syntrophy; cryptic cycling; and microbial production and consumption of greenhouse gases.
We encourage studies linking hydrological dynamics to geomicrobiological processes, including effects of groundwater flow, fluid mixing, connectivity, and redox fluctuations on microbial activity, reaction fronts, and biogeochemical hotspots. Applications to groundwater quality, contaminant attenuation, geological carbon storage, underground hydrogen storage, radioactive-waste disposal, and subsurface resource recovery are also within scope, as are studies of early Earth analogues and extraterrestrial habitability.
We welcome interdisciplinary approaches combining field observations, cultivation, multi-omics, isotope tracing, microscale imaging, mineralogical characterization, electrochemical measurements, and reactive transport modelling. By bringing together microbiologists, geochemists, mineralogists, hydrologists, biogeochemists, and planetary scientists, this session aims to advance a predictive understanding of subsurface life and its role in Earth-system biogeochemistry.