Gibbs Energy Dynamic Yield Method (GEDYM): Predicting microbial growth yields under energy-limiting conditions

Journal Article · Thu Nov 01 00:00:00 EDT 2018 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/j.gca.2018.08.023· OSTI ID:1469223

Smeaton, Christina M.; Van Cappellen, Philippe

Biomass-explicit biogeochemical models assign microbial growth yields (Y) using values measured in the laboratory or predicted using thermodynamics-based methods. However, Y values are rarely measured under the low energy delivery conditions that often prevail in the subsurface, and existing predictive methods for calculating Y values when the catabolic energy supply rate is limited remain poorly tested. Here, we derive and validate a new semi-theoretical method for calculating Y values: the Gibbs Energy Dynamic Yield Method (GEDYM). Method validation relies on a compilation of 132 geochemically relevant literature Y values comprising predominantly (60%) low energy (> -25 kJ (mol ^e-)^-1) metabolisms. GEDYM is based on estimating the Gibbs energy change of the metabolic reaction ($$\Delta G_{met}$$), which links the Gibbs energy changes of the catabolic ($$\Delta G_{cat}$$) and anabolic ($$\Delta G_{an}$$) reactions of a microorganism through its growth yield. Given that the values of $$\Delta G_{met}$$, $$\Delta G_{cat}$$ and $$\Delta G_{an}$$ all depend on their respective reaction quotients, the resulting Y values account for changes in the chemical environment surrounding the cells. GEDYM incorporates an empirical relationship that accurately estimates the extent to which $$\Delta G_{met}$$ deviates from its standard state value from the relative difference between $$\Delta G_{cat}$$ and its corresponding standard state value. GEDYM yields Y values with lower relative errors and statistical bias than the existing Gibbs energy dissipation method (GEDM). Using dissimilatory iron reduction, sulfate reduction and methanogenesis as examples, we illustrate the importance of considering variations in $$\Delta G_{cat}$$ and $$\Delta G_{an}$$ when predicting Y values for individual metabolisms. Because of its ability to dynamically adjust the values of $$\Delta G_{met}$$ and Y to variable geochemical conditions, GEDYM yields a more realistic representation of geomicrobial activity in predictive reactive transport models.

• Research Organization: Georgia Institute of Technology, Atlanta, GA (United States)
• Sponsoring Organization: USDOE Office of Science (SC); Canada Excellence Research Chair (CERC); Global Water Futures (GWF)
• Grant/Contract Number: SC0005520
• OSTI ID: 1469223
• Alternate ID(s): OSTI ID: 1610844
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Vol. 241 Journal Issue: C; ISSN 0016-7037
• Publisher: Elsevier; The Geochemical Society; The Meteoritical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
geochemistry & geophysics