Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock

Area of Science:

• Geomicrobiology
• Environmental Science
• Nuclear Waste Management

Background:

• Opalinus Clay is designated for geological nuclear waste repositories in Switzerland.
• Hydrogen gas production from steel corrosion poses a risk to repository integrity.
• Understanding microbial roles in deep subsurface environments is crucial for safety assessments.

Purpose of the Study:

• To investigate microbial hydrogen consumption in the Opalinus Clay.
• To characterize the microbial community and its metabolic functions.
• To assess the potential of microbial processes for mitigating gas pressure buildup in repositories.

Main Methods:

• In situ experiment conducted at the Mont Terri Underground Rock Laboratory.
• Metagenomic binning to identify microbial populations.
• Metaproteomic analysis to determine active metabolic pathways.

Main Results:

• Microbial communities actively consume hydrogen, fueled by its production from steel corrosion.
• A novel carbon cycle was identified, driven by autotrophic hydrogen oxidizers and completed by sulfate-reducing bacteria.
• The study revealed a complex microbial metabolic web involving novel genera.

Conclusions:

• Opalinus Clay harbors a chemolithoautotrophic-based microbial system capable of consuming hydrogen.
• The identified microbial carbon cycle can be integrated into geological repository design to reduce pressure.
• This research provides a model for microbial carbon cycling in hydrogen and sulfate-rich deep subsurface environments.