Propionate is typically degraded by syntrophic associations between anaerobic bacteria and hydrogenotrophic partner, due that the microorganism have to confront unfavourable energetics processes (ΔG0’= +76 kJ/reaction), where the bacteria only can degrade it when the concentration of the products (H2 and formate) are kept low. Syntrophy is defined as an association between two or more microorganisms as an strategy to defeat the thermodynamic constrains of the degradation of certain compounds. Propionate and butyrate are key intermediates in the anaerobic conversion of complex organic materials. Syntrophic propionate-degrading bacteria rely on the presence of a hydrogenotrophic partner for growth. Most commonly, hydrogenotrophic methanogens are used as syntrophic partners; however, sulfate reducers bacteria (SRB), such as Desulfovibrio species, are commonly found in methanogenic environments and their role is not completely understood. Cultivation, FISH and cytometry techniques will be performed to understand better the interactions between these microorganisms. Proteomics studies will be performed for getting more insight into the physiology of the bi- and tri-cultures studies in this task.
Figure 1. A) Cultivation experimental design B) Tri-culture of P. schinkii (yellow), D. desulfuricans (green) and M. hungatei (blue). C) Theoretical scheme of syntrophic interaction between P. schinkii, D. desulfuricans and M. hungatei.