Covariation of hot spring geochemistry with microbial genomic diversity, function, and evolution

Area of Science:

• Astrobiology
• Geomicrobiology
• Evolutionary Biology

Background:

• The geosphere and microbial biosphere have co-evolved for billions of years, with hydrothermal habitats proposed as the origin of life.
• The degree to which modern thermophiles and their habitats resemble early Earth conditions is not well understood.

Purpose of the Study:

• To investigate the relationship between hot spring geochemistry and microbial communities.
• To identify potential analogs for early Earth hydrothermal habitats.

Main Methods:

• Geochemical analysis of 64 analytes from 34 high-temperature springs in Yellowstone National Park.
• Generation and analysis of 1022 metagenome-assembled genomes (MAGs) from these springs.
• Integration with 444 MAGs from 35 published metagenomes to assess microbial community structure and function.

Main Results:

• Microbial communities (MAGs) and their metabolic functions are distinctly distributed across pH gradients.
• Acidic or circumneutral/alkaline springs host later-branching MAGs with oxygen-dependent metabolisms, unlike early Earth conditions.
• Moderately acidic springs contain earlier-branching MAGs with anaerobic, gas-dependent metabolisms, consistent with early life hypotheses.

Conclusions:

• Redox state significantly influences the eco-evolutionary dynamics between thermophiles and their environments.
• Moderately acidic, volcanically sourced hot springs in Yellowstone serve as valuable analogs for early Earth hydrothermal habitats.