A global perspective on bacterial diversity in the terrestrial deep subsurface.

Area of Science:

• Microbiology
• Geomicrobiology
• Environmental Science

Background:

• The terrestrial deep subsurface represents a vast, under-explored biome, potentially holding 12-20% of Earth's biomass.
• Previous studies focused on surface and marine habitats, leaving terrestrial deep subsurface microbial diversity poorly understood.
• A broader understanding of microbial communities and their environmental drivers in this deep biosphere is needed.

Approach:

• A meta-analysis of existing metagenomic studies was performed to assess microbial diversity in the terrestrial deep subsurface.
• The study analyzed microbial communities across various localities, depths, and aquifer lithologies.
• An in silico contamination-aware approach was employed to ensure data robustness.

Key Points:

• Terrestrial deep subsurface microbiota are primarily composed of Betaproteobacteria, Gammaproteobacteria, and Firmicutes, likely due to their metabolic versatility.
• A conserved core community of Betaproteobacteria and Gammaproteobacteria operational taxonomic units was identified across different locations.
• This suggests a resilient microbial community structure independent of specific environmental variables like lithology or depth.

Conclusions:

• A core microbial community appears to be prevalent in the terrestrial deep subsurface, potentially vital for habitat colonization and maintenance.
• Robust downstream analysis methods are critical for reliable conclusions from deep subsurface sequencing data.
• Characterizing deep terrestrial subsurface microbial diversity is essential for understanding global subsurface element and nutrient cycling.