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ISME J. 2020 Jan 29. doi: 10.1038/s41396-020-0595-5. [Epub ahead of print]

From an extremophilic community to an electroautotrophic production strain: identifying a novel Knallgas bacterium as cathodic biofilm biocatalyst.

Author information

1
Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 2, 76131, Karlsruhe, Germany.
2
Engler-Bunte-Institute, Chair of Water Chemistry and Water Technology, Karlsruhe Institute of Technology (KIT), Engler-Bunte-Ring 1-7, 76131, Karlsruhe, Germany.
3
Center for Environmental Research and Sustainable Technology (UFT), University of Bremen, Leobener Strasse 6, 28359, Bremen, Germany.
4
Max Rubner-Institute, Federal Research Institute of Nutrition and Food, Haid-und-Neu-Straße 9, 76131, Karlsruhe, Germany.
5
Institute of Functional Interfaces, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
6
TZW: DVGW-Technologiezentrum Wasser, Karlsruher Straße 84, 76139, Karlsruhe, Germany.
7
Institute of Geography and Geoecology, Karlsruhe Institute of Technology (KIT), Reinhard-Baumeister-Platz 1, 76131, Karlsruhe, Germany.
8
Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 2, 76131, Karlsruhe, Germany. Johannes.gescher@kit.edu.
9
Institute for Biological Interfaces, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany. Johannes.gescher@kit.edu.

Abstract

Coupling microbial electrosynthesis to renewable energy sources can provide a promising future technology for carbon dioxide conversion. However, this technology suffers from a limited number of suitable biocatalysts, resulting in a narrow product range. Here, we present the characterization of the first thermoacidophilic electroautotrophic community using chronoamperometric, metagenomic, and 13C-labeling analyses. The cathodic biofilm showed current consumption of up to -80 µA cm-2 over a period of 90 days (-350 mV vs. SHE). Metagenomic analyses identified members of the genera Moorella, Desulfofundulus, Thermodesulfitimonas, Sulfolobus, and Acidianus as potential primary producers of the biofilm, potentially thriving via an interspecies sulfur cycle. Hydrogenases seem to be key for cathodic electron uptake. An isolation campaign led to a pure culture of a Knallgas bacterium from this community. Growth of this organism on cathodes led to increasing reductive currents over time. Transcriptomic analyses revealed a distinct gene expression profile of cells grown at a cathode. Moreover, pressurizable flow cells combined with optical coherence tomography allowed an in situ observation of cathodic biofilm growth. Autotrophic growth was confirmed via isotope analysis. As a natural polyhydroxybutyrate (PHB) producer, this novel species, Kyrpidia spormannii, coupled the production of PHB to CO2 fixation on cathode surfaces.

PMID:
31996786
DOI:
10.1038/s41396-020-0595-5

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