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Minireview: demystifying microbial reaction energetics
Author(s) -
Amend Jan P.,
LaRowe Douglas E.
Publication year - 2019
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.14778
Subject(s) - gibbs free energy , energetics , methanogenesis , biology , anaerobic exercise , anaerobic respiration , redox , environmental chemistry , biochemical engineering , ecology , thermodynamics , chemistry , methane , inorganic chemistry , physiology , physics , engineering
Summary The biology literature is rife with misleading information on how to quantify catabolic reaction energetics. The principal misconception is that the sign and value of the standard Gibbs energy ( Δ G r 0 ) define the direction and energy yield of a reaction; they do not. Δ G r 0 is one part of the actual Gibbs energy of a reaction ( ΔG r ), with a second part accounting for deviations from the standard composition. It is also frequently assumed that Δ G r 0 applies only to 25 °C and 1 bar; it does not. Δ G r 0 is a function of temperature and pressure. Here, we review how to determine ΔG r as a function of temperature, pressure and chemical composition for microbial catabolic reactions, including a discussion of the effects of ionic strength on ΔG r and highlighting the large effects when multi‐valent ions are part of the reaction. We also calculate ΔG r for five example catabolisms at specific environmental conditions: aerobic respiration of glucose in freshwater, anaerobic respiration of acetate in marine sediment, hydrogenotrophic methanogenesis in a laboratory batch reactor, anaerobic ammonia oxidation in a wastewater reactor and aerobic pyrite oxidation in acid mine drainage. These examples serve as templates to determine the energy yields of other catabolic reactions at environmentally relevant conditions.