Thermodynamics Underpinning the Microbial Community-Level Nitrogen Energy Metabolism

Area of Science:

• Microbial metabolism
• Biogeochemical cycles
• Biochemistry

Background:

• Nitrogen compounds are vital electron donors/acceptors in microbial energy metabolism and biogeochemical cycles.
• The thermodynamic favorability of nitrogen redox reactions may have influenced the evolution of microbial energy metabolism, but the extent is unknown.

Purpose of the Study:

• To quantitatively assess the similarity between energetically superior nitrogen reactions and the nitrogen community-level metabolic network.
• To understand the role of thermodynamics in shaping microbial metabolic networks.

Main Methods:

• Identified 988 theoretically plausible nitrogen reactions.
• Evaluated the energetic favorability of these reactions.
• Reconstructed the nitrogen community-level network from enzymatic reactions.
• Quantitatively compared the energetically superior reactions with the community network.

Main Results:

• Significant overlap was observed between energetically superior nitrogen reactions and the community-level metabolic network.
• Composite enzymatic reactions showed higher alignment with energetically superior reactions than individual reactions.

Conclusions:

• Thermodynamic favorability of redox reactions acts as a selective pressure at the species or community level.
• Thermodynamics critically influences microbial metabolic networks and overall ecosystem functioning.