Segregation of the Anodic Microbial Communities in a Microbial Fuel Cell Cascade


Metabolic interactions within microbial communities are essential forthe efficient degradation of complex organic compounds, and underpin naturalphenomena driven by microorganisms, such as the recycling of carbon-,nitrogen-, and sulfur-containing molecules. These metabolic interactionsultimately determine the function, activity and stability of the community, andtherefore their understanding would be essential to steer processes wheremicrobial communities are involved. This is exploited in the design ofmicrobial fuel cells (MFCs), bioelectrochemical devices that convert thechemical energy present in substrates into electrical energy through themetabolic activity of microorganisms, either single species or communities. Inthis work, we analyzed the evolution of the microbial community structure in acascade of MFCs inoculated with an anaerobic microbial community andcontinuously fed with a complex medium. The analysis of the composition of theanodic communities revealed the establishment of different communities in theanodes of the hydraulically connected MFCs, with a decrease in the abundance offermentative taxa and a concurrent increase in respiratory taxa along thecascade. The analysis of the metabolites in the anodic suspension showed a metabolicshift between the first and last MFC, confirming the segregation of the anodiccommunities. Those results suggest a metabolic interaction mechanism betweenthe predominant fermentative bacteria at the first stages of the cascade andthe anaerobic respiratory electrogenic population in the latter stages, whichis reflected in the observed increase in power output. We show that ourexperimental system represents an ideal platform for optimization of processeswhere the degradation of complex substrates is involved, as well as a potentialtool for the study of metabolic interactions in complex microbial communities.

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