A hydrogen-based subsurface microbial community dominated by methanogens

Area of Science:

• Astrobiology
• Microbial Ecology
• Geochemistry

Background:

• The search for extraterrestrial life may benefit from studying Earth-based ecosystems analogous to conditions on other planets.
• Geochemical and thermodynamic models suggest geologically derived hydrogen could support subsurface microbial life on Mars and Europa, with methanogens forming the ecosystem base.

Purpose of the Study:

• To identify and characterize a subsurface microbial community that could serve as an analogue for potential extraterrestrial ecosystems.
• To investigate the primary energy source and dominant microorganisms within this unique subsurface environment.

Main Methods:

• Analysis of 16S ribosomal DNA sequences from microbial communities in deep subsurface hydrothermal waters.
• Geochemical characterization of the water to determine the available energy sources.

Main Results:

• A unique subsurface microbial community was discovered where hydrogen-consuming, methane-producing Archaea significantly outnumbered Bacteria.
• Over 90% of identified microbial sequences were related to hydrogen-using methanogenic microorganisms.
• Geochemical analysis confirmed geothermal hydrogen, not organic carbon, as the primary energy source for this community.

Conclusions:

• Hydrogen-based methanogenic microbial communities exist in Earth's subsurface.
• This finding provides a viable analogue for potential subsurface life on other planets like Mars and Europa.
• The dominance of Archaea in such environments highlights a potential model for extraterrestrial microbial ecosystems.