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Plenary Lecture 15: Can bioenergetics tell us more about microbial ecosystems activity than community identity?

Friday 28th November 2014 - 10:05 to 10:40
INI Seminar Room 1
Co-authors: Rebeca González-Cabaleiro (University of Santiago de Compostela (ES)), Robbert Kleerebezem (Delft University of Technology (NL)), Juan M. Lema (University of Santiago de Compostela (ES))

Bioenergetic considerations appear to play a central role in defining microbial ecosystems activity irrespective of the microbial community identity. Our modelling results suggest that mainly bioenergetics can define the activity of microbial ecosystems at three different levels: (1) When a generalized bioenergy-based model is used to describe the competition between a number of existing and postulated microbial metabolisms, the prevailing successful ones, the reasons behind their success and some syntrophisms are correctly predicted. This has been applied to glucose fermentation and to nitrogen oxidation and reduction ecosystems. Metabolic activities appear to be selected by maximum energy harvest rate. Based on this we postulate that it is primarily energetics who defined the today existing microbial metabolisms, pathway lengths and synergisms among them. (2) When specific anaerobic fermentative reactions of interest are studied under a thermodynamic perspective, conclusions can be drawn out about their potential reversibility. Quasi equilibrium calculations can be used to estimate concentration limits for the feasibility of pathway steps and compares with physiological and kinetic limits. Based on this we postulate that in energy limited microbial ecosystems, thermodynamic limitations can impose unfeasible intermediate metabolite concentrations rendering a metabolic pathway impossible or reversing it. (3) When anaerobic fermentation microbial ecosystems are described as one mass and electron balanced metabolic network, an optimisation of the network for maximum energy yield can provide an accurate prediction of the product formation. This has been successfully applied to the prediction of products and their shifts as a function of the environmental pH. Based on this we postulate that in energy limited microbial ecosystems such as fermentations, a bioenergetic maximum energy harvest rate criteria defines the product spectrum irrespective of the microbial community.

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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons