Functional universality in slow-growing microbial communities arises from thermodynamic constraints

TL;DR

This paper presents a thermodynamics-based model explaining how microbial communities in energy-limited environments exhibit functional convergence regardless of species composition, driven by thermodynamic constraints and maximum heat dissipation.

Contribution

The study introduces a novel consumer-resource model incorporating thermodynamic constraints, revealing universal community function and structure driven by thermodynamic principles.

Findings

Community function converges despite taxonomic differences.

Thermodynamic constraints lead to similar community structures.

Community metabolism is governed by maximum heat dissipation.

Abstract

The dynamics of microbial communities is incredibly complex, determined by competition for metabolic substrates and cross-feeding of byproducts. Species in the community grow by harvesting energy from chemical reactions that transform substrates to products. In many anoxic environments, these reactions are close to thermodynamic equilibrium and growth is slow. To understand the community structure in these energy-limited environments, we developed a microbial community consumer-resource model incorporating energetic and thermodynamic constraints on an interconnected metabolic network. The central ingredient of the model is product inhibition, meaning that microbial growth may be limited not only by depletion of metabolic substrates but also by accumulation of products. We demonstrate that these additional constraints on microbial growth cause a convergence in the structure and function of the community metabolic network -- independent of species composition and biochemical details -- providing a possible explanation for convergence of community function despite taxonomic variation observed in many natural and industrial environments. Furthermore, we discovered that the structure of community metabolic network is governed by the thermodynamic principle of maximum heat dissipation. Overall, the work demonstrates how universal thermodynamic principles may constrain community metabolism and explain observed functional convergence in microbial communities.