Serpentinization-Influenced Groundwater Harbors Extremely Low Diversity Microbial Communities Adapted to High pH

Area of Science:

• Geomicrobiology
• Biogeochemistry
• Environmental Science

Background:

• Serpentinization of ultramafic rocks creates unique subsurface environments.
• These environments offer reductants but pose challenges like high pH and limited electron acceptors.
• Previous studies indicated low microbial abundance and diversity in serpentinites.

Purpose of the Study:

• To comprehensively analyze microbial communities in serpentinite-influenced subsurface aquifers.
• To identify physicochemical factors driving microbial activity and community structure.
• To elucidate the metabolic potential of microorganisms in hyperalkaline groundwater.

Main Methods:

• Sampling from seven wells in serpentinite aquifers.
• Analysis of solute and gas chemistry.
• Microbial diversity assessment using 16S rRNA gene sequencing.
• Metabolic potential determination via shotgun metagenomics.

Main Results:

• Environmental factors like pH, methane, and carbon monoxide correlate with microbial communities.
• Betaproteobacteria and Clostridia were dominant in highly serpentinized fluids.
• Metagenomes revealed pathways for hydrogen metabolism, carbon monoxide oxidation, carbon fixation, and acetogenesis.

Conclusions:

• Specific microbial groups, particularly Betaproteobacteria and Clostridia, are adapted to serpentinizing groundwater ecosystems.
• These microbes play crucial roles in hydrogen and carbon cycling.
• The study provides a foundation for understanding biogeochemical processes in serpentinite subsurface environments.