Isolation of the exoelectrogenic denitrifying bacterium Comamonas denitrificans based on dilution to extinction |
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Authors: | Defeng Xing Shaoan Cheng Bruce E Logan John M Regan |
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Institution: | (1) Engineering Environmental Institute, The Pennsylvania State University, 212 Sackett Building, University Park, PA 16802, USA;(2) Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, University Park, PA 16802, USA; |
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Abstract: | The anode biofilm in a microbial fuel cell (MFC) is composed of diverse populations of bacteria, many of whose capacities
for electricity generation are unknown. To identify functional populations in these exoelectrogenic communities, a culture-dependent
approach based on dilution to extinction was combined with culture-independent community analysis. We analyzed the diversity
and dynamics of microbial communities in single-chamber air-cathode MFCs with different anode surfaces using denaturing gradient
gel electrophoresis based on the 16S rRNA gene. Phylogenetic analyses showed that the bacteria enriched in all reactors belonged
primarily to five phylogenetic groups: Firmicutes, Actinobacteria, α-Proteobacteria, β-Proteobacteria, and γ-Proteobacteria. Dilution-to-extinction experiments further demonstrated that Comamonas denitrificans and Clostridium aminobutyricum were dominant members of the community. A pure culture isolated from an anode biofilm after dilution to extinction was identified
as C. denitrificans DX-4 based on 16S rRNA sequence and physiological and biochemical characterizations. Strain DX-4 was unable to respire using
hydrous Fe(III) oxide but produced 35 mW/m2 using acetate as the electron donor in an MFC. Power generation by the facultative C. denitrificans depends on oxygen and MFC configuration, suggesting that a switch of metabolic pathway occurs for extracellular electron
transfer by this denitrifying bacterium. |
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