Major phylum-level differences between porefluid and host rock bacterial communities in the terrestrial deep...

Area of Science:

• Microbiology
• Geomicrobiology
• Deep Biosphere Research

Background:

• The deep subsurface biosphere harbors diverse microorganisms, yet accessing these environments for study is challenging.
• Understanding microbial ecology in deep terrestrial habitats is crucial for comprehending Earth's biogeochemical cycles.

Purpose of the Study:

• To investigate bacterial diversity within deep subsurface fracture fluids and host rock at the Sanford Underground Research Facility (SURF).
• To compare microbial communities from fracture fluids and host rock to understand their ecological separation.

Main Methods:

• DNA extraction from deep groundwater and host rock samples collected at 1.45 km depth.
• 16S rRNA gene pyrotag sequencing to analyze bacterial community composition.
• Comparative analysis with microbial data from five other terrestrial subsurface sites.

Main Results:

• Diverse microbial communities, including chemolithoautotrophs, heterotrophs, and candidate phyla, were identified.
• A distinct separation was observed between microbial communities in fracture fluids and those in host rock.
• Classes Clostridia and Betaproteobacteria were dominant in terrestrial subsurface fluids across multiple sites.

Conclusions:

• Microbial communities in deep subsurface fracture fluids and host rocks are significantly different, indicating distinct ecological niches.
• This study provides unique insights into the spatial distribution and differentiation of microbial life within deep terrestrial subsurface environments.