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Communication Dans Un Congrès Année : 2018

Rumen methanogens display species-specific energetic and growth dynamics: a thermodynamic and kinetic based modelling approach

Résumé

Rumen methanogenic archaea are specialized microbes that play a central role in rumen metabolism. In the rumen, the degradation and further fermentation of plant polysaccharides are orchestrated by syntrophic interactions that include hydrogen transfer from bacteria and protozoa to archaea. By lowering the concentration of hydrogen in the rumen, methanogenic archaea favour fermentation thermodynamics and enhance substrate utilization by fermenting microbes. However, in this process, methanogens produce methane, a major greenhouse gas whose production represents a loss of energy for the animal and contributes importantly to the environmental footprint of the livestock sector. To enhance the understanding of rumen methanogenesis, some key aspects that need to be elucidated include (i) the relationship between the methanogens community structure and the ruminant methane production, (ii) the ecological factors that drive interactions of methanogens within the methanogenic community and with other rumen microbes, and (iii) the rate and extent of the methanogenesis performed by the rumen archaea. This work was centred on the latter aspect. Our purpose was to quantitatively characterize the dynamics of hydrogen utilization, methane production, growth and heat flux of three representative rumen methanogens by integrating thermodynamics, microbiology and mathematical modelling. In vitro growth experiments were performed with Methanobrevibacter ruminantium, Methanobrevibacter smithii and Methanobacterium formicium in Balch tubes at 39°C with a gas mix of H2/CO2 as substrates. Microbial growth was quantified by measuring the OD660 and the functional gene mcrA using qPCR. Gas composition was determined by chromatography. Thermodynamic experiments with the three methanogens were performed in isothermal microcalorimeters to quantify the methanogenesis heat flux. Experimental data revealed species-specific metabolism kinetics and energetic dynamics among rumen methanogens. A dynamic model with an energetic-based kinetic function was constructed and calibrated with the experimental data from growth experiments. The resulting model captured efficiently the dynamics of methanogens metabolism and allows quantifying kinetic differences between the three rumen methanogens studied. By detailing methanogens dynamics, this work will be instrumental for constructing novel rumen models with enhanced prediction capabilities. This enhanced understanding of rumen methanogens could be useful, in the future, to devise new strategies for methane mitigation from ruminant livestock.
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Dates et versions

hal-01840971 , version 1 (16-07-2018)

Identifiants

  • HAL Id : hal-01840971 , version 1
  • PRODINRA : 426587

Citer

Rafael Munoz Tamayo, Milka Popova, Diego Morgavi, Dominique Graviou, Jean-Pierre Morel, et al.. Rumen methanogens display species-specific energetic and growth dynamics: a thermodynamic and kinetic based modelling approach. Journées d'Animation Scientifique du département PHASE, Institut National de Recherche Agronomique (INRA). UAR Département Physiologie Animale et Systèmes d'Elevage (0558)., Apr 2018, Rennes, France. ⟨hal-01840971⟩
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