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Hydrogen-driven subsurface lithoautotrophic microbial ecosystems (SLiMEs): do they exist and why should we care?
Kenneth H Nealson1, Fumio Inagaki, Ken Takai
1Department of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089-0740, USA. knealson@usc.edu
Trends in Microbiology
|August 2, 2005
Summary
Subsurface lithoautotrophic microbial ecosystems (SLiMEs) may exist independently of photosynthesis. Evidence suggests these hydrogen-driven communities are crucial for understanding Earth's deep biosphere and the search for extraterrestrial life.
Area of Science:
- Microbiology
- Geochemistry
- Astrobiology
Background:
- Syntrophic intercellular hydrogen transfer is vital for anaerobic ecosystems.
- Microorganisms utilize hydrogen as an energy source via uptake hydrogenases.
- The existence of subsurface lithoautotrophic microbial ecosystems (SLiMEs) independent of photosynthesis is debated.
Purpose of the Study:
- To investigate the existence and persistence of SLiMEs independent of photosynthetic products.
- To assess the implications of SLiMEs for understanding Earth's subsurface and extraterrestrial life.
Main Methods:
- Analysis of microbial community structures and metabolic pathways in deep subsurface environments.
- Isotopic tracing to determine the origin of energy sources for microbial communities.
- Geochemical modeling to simulate long-term ecosystem function.
Main Results:
- Growing evidence supports the existence of SLiME-like communities.
- These communities appear capable of long-term independence from photosynthesis.
- Hydrogen transfer is a key process enabling these ecosystems.
Conclusions:
- SLiMEs likely exist and play a significant role in Earth's deep biosphere.
- The discovery of SLiMEs has profound implications for astrobiology and the search for life beyond Earth.
- Further research is needed to unequivocally establish the long-term independence of SLiMEs from photosynthesis.