About this Research Topic
Organisms inhabiting the terrestrial deep biosphere are confronted with numerous intersecting conditions that likely limit their diversity, abundance, and activity including extremes of temperature, pH, and pressure, as well as low nutrient concentration and flux, anaerobicity, and limited energy availability. Estimates of biomass in the subsurface vary, and existing estimates derive primarily from studies of marine systems. It is becoming clear, however, that the terrestrial deep biosphere not only hosts considerable biomass planet-wide, but that this biomass has a direct impact on surface processes and global biogeochemical cycles both today, and in Earth’s past. This Research Topic in Frontiers in Microbiology, Extreme Microbiology provides a forum for bringing together results pertinent to terrestrial deep biosphere ecosystems, including [but not limited to] ecosystems partially or fully closed to photosynthetically derived energy and carbon, hot and cold springs, aquifers, deep fracture fluids, cave and mine systems, and sub-ice habitats. Each of the above “portals” affords the unique opportunity to examine the collective environmental parameters that shape the microbial community composition, abundance, and function of the deep biosphere, information which must be considered in concert in order to assess the contribution of these systems to global biogeochemical cycles. Of equal interest are experimental studies of the environmental conditions or the responses of microorganisms to environmental pressures found in terrestrial deep biosphere ecosystems.
An effort to consolidate up to date research concerning the terrestrial deep biosphere is of critical importance as rates of primary production, energy flux, and elemental cycling in the deep biosphere are still virtual unknowns. Further, the connectivity between surface processes and deep biosphere processes may include the seeding of surface environments with “legacy” subsurface genetic material. This Research Topic will address these issues, focusing on evidence and implications of connection between the geosphere, hydrosphere, and biosphere of terrestrial deep subsurface habitats.
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.