title: Resilience, Dynamics, and Interactions within a Model Multispecies Exoelectrogenic-Biofilm Community.
abstract: Anode-associated multispecies exoelectrogenic biofilms are essential for the function of bioelectrochemical systems (BESs). The individual activities of anode-associated organisms and physiological responses resulting from coculturing are often hard to assess due to the high microbial diversity in these systems. Therefore, we developed a model multispecies biofilm comprising three exoelectrogenic proteobacteria,Shewanella oneidensis,Geobacter sulfurreducens, andGeobacter metallireducens, with the aim to study in detail the biofilm formation dynamics, the interactions between the organisms, and the overall activity of an exoelectrogenic biofilm as a consequence of the applied anode potential. The experiments revealed that the organisms build a stable biofilm on an electrode surface that is rather resilient to changes in the redox potential of the anode. The community operated at maximum electron transfer rates at electrode potentials that were higher than 0.04 V versus a normal hydrogen electrode. Current densities decreased gradually with lower potentials and reached half-maximal values at -0.08 V. Transcriptomic results point toward a positive interaction among the individual strains.S. oneidensisandG. sulfurreducensupregulated their central metabolisms as a response to cultivation under mixed-species conditions.G. sulfurreducenswas detected in the planktonic phase of the bioelectrochemical reactors in mixed-culture experiments but not when it was grown in the absence of the other two organisms.IMPORTANCEIn many cases, multispecies communities can convert organic substrates into electric power more efficiently than axenic cultures, a phenomenon that remains unresolved. In this study, we aimed to elucidate the potential mutual effects of multispecies communities in bioelectrochemical systems to understand how microbes interact in the coculture anodic network and to improve the community's conversion efficiency for organic substrates into electrical energy. The results reveal positive interactions that might lead to accelerated electron transfer in mixed-species anode communities. The observations made within this model biofilm might be applicable to a variety of nonaxenic systems in the field.
authors.affiliation: Institute for Applied Biosciences, Department of Applied Biology, Karlsruhe Institute of Technology, Karlsruhe, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Prokhorova
authors.affiliation: Institute for Applied Biosciences, Department of Applied Biology, Karlsruhe Institute of Technology, Karlsruhe, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Sturm-Richter
authors.affiliation: Institute of Functional Interfaces, Department of Interface Microbiology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany.
authors.forename: Andreas
authors.identifier: http://orcid.org/0000-0001-9086-2584
authors.initials: A
authors.lastname: Doetsch
authors.affiliation: Institute for Applied Biosciences, Department of Applied Biology, Karlsruhe Institute of Technology, Karlsruhe, Germany johannes.gescher@kit.edu.|Institute for Biological Interfaces, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Gescher
mesh_terms: D001674:Bioelectric Energy Sources / Q000382:microbiology*; D018441:Biofilms / Q000254:growth & development*; D018920:Coculture Techniques; D004560:Electricity; D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes / Q000382:microbiology; D004579:Electron Transport; D045302:Geobacter / Q000254:growth & development / Q000378:metabolism*; D010084:Oxidation-Reduction; D020592:Shewanella / Q000254:growth & development / Q000378:metabolism*
keywords: Geobacter; Shewanella; bioelectrochemical systems; exoelectrogenic biofilm; transcriptome analysis