Genetic diversity in terrestrial subsurface ecosystems impacted by geological degassing

Area of Science:

• Geochemistry
• Microbiology
• Deep Biosphere Research

Background:

• Earth's mantle releases significant amounts of carbon dioxide (CO2) and other gases, influencing microbial ecosystems globally.
• The impact of mantle degassing on microbial life in non-thermal deep subsurface environments remains largely unexplored.

Purpose of the Study:

• To investigate the microbial community and geochemical characteristics of a cold-water geyser system fueled by mantle degassing.
• To compare deep subsurface microbial communities and identify adaptations related to geological degassing.

Main Methods:

• Comparative metagenomics of deep subsurface fluids.
• Geochemical measurements.
• In silico replication analysis of microbial communities.

Main Results:

• Identified key organisms, including uncultivated Candidatus Altiarchaeum, exhibiting global biogeographic patterns and site-specific adaptations.
• Demonstrated conserved chemolithoautotrophic metabolism across 17 deep subsurface sites.
• Observed a linear relationship between bacterial replication and ecosystem depth, except in sites impacted by geological degassing.

Conclusions:

• Subsurface ecosystems influenced by geological degassing are significant hotspots for microbial life.
• Gene loss and horizontal gene transfer play crucial roles in microbial adaptation to deep subsurface environments.
• Mantle degassing shapes microbial metabolism and community structure in the deep biosphere.