Using thermodynamics to obtain geochemical information from genomes.

Area of Science:

• Geosciences
• Biogeochemistry
• Evolutionary Biology
• Thermodynamics

Background:

• Thermodynamic characterization of chemical stabilities is crucial in geosciences.
• Genomic analysis using thermodynamic models can illuminate genome-geochemical environment relationships.
• Previous studies have explored evolutionary adaptation to varying redox conditions in prokaryotes.

Purpose of the Study:

• To present a chemical and thermodynamic analysis of prokaryotic lineages.
• To quantify the effects of hydrogen activity (aH2) and temperature on organic compound stability.
• To apply these techniques to reference proteomes for methanogens and Thaumarchaeota.

Main Methods:

• Developed a thermodynamic model quantifying the influence of hydrogen activity and temperature on organic compound stability.
• Applied thermodynamic analysis to reference proteomes of methanogens (Class I and II) and Thaumarchaeota.
• Calculated specific aH2 and temperature conditions for proteome stability.

Main Results:

• Identified aH2 and temperature ranges for the relative stability of methanogen reference proteomes.
• Calculated aH2 values align with measured habitats of methanogens, from highly reducing to less reducing environments.
• The transition between basal and terrestrial Thaumarchaeota occurs at a less-reducing redox boundary compared to methanogen classes.

Conclusions:

• Energy minimization is a significant driver of evolution.
• Geochemical calculations involving biomolecules can quantify the coevolution of the geosphere and biosphere.
• Thermodynamic modeling provides a framework for understanding evolutionary adaptations to geochemical environments.