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Convergent development of anodic bacterial communities in microbial fuel cells.

Yates MD, Kiely PD, Call DF, Rismani-Yazdi H, Bibby K, Peccia J, Regan JM, Logan BE - ISME J (2012)

Bottom Line: After 16 cycles the predominance of Geobacter spp. in anode communities was identified using 16S rRNA gene clone libraries (58±10%), fluorescent in-situ hybridization (FISH) (63±6%) and pyrosequencing (81±4%).While the clone library analysis for the underperforming UAJA3 had a significantly lower percentage of Geobacter spp. sequences (36%), suggesting that a predominance of this microbe was needed for convergent power densities, the lower percentage of this species was not verified by FISH or pyrosequencing analyses.These results show that the predominance of Geobacter spp. in acetate-fed systems was consistent with good MFC performance and independent of the inoculum source.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, USA.

ABSTRACT
Microbial fuel cells (MFCs) are often inoculated from a single wastewater source. The extent that the inoculum affects community development or power production is unknown. The stable anodic microbial communities in MFCs were examined using three inocula: a wastewater treatment plant sample known to produce consistent power densities, a second wastewater treatment plant sample, and an anaerobic bog sediment. The bog-inoculated MFCs initially produced higher power densities than the wastewater-inoculated MFCs, but after 20 cycles all MFCs on average converged to similar voltages (470±20 mV) and maximum power densities (590±170 mW m(-2)). The power output from replicate bog-inoculated MFCs was not significantly different, but one wastewater-inoculated MFC (UAJA3 (UAJA, University Area Joint Authority Wastewater Treatment Plant)) produced substantially less power. Denaturing gradient gel electrophoresis profiling showed a stable exoelectrogenic biofilm community in all samples after 11 cycles. After 16 cycles the predominance of Geobacter spp. in anode communities was identified using 16S rRNA gene clone libraries (58±10%), fluorescent in-situ hybridization (FISH) (63±6%) and pyrosequencing (81±4%). While the clone library analysis for the underperforming UAJA3 had a significantly lower percentage of Geobacter spp. sequences (36%), suggesting that a predominance of this microbe was needed for convergent power densities, the lower percentage of this species was not verified by FISH or pyrosequencing analyses. These results show that the predominance of Geobacter spp. in acetate-fed systems was consistent with good MFC performance and independent of the inoculum source.

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DDGE gel from cycle 16 showing bands that were excised and identified. Gels were used in the PCA to monitor shifts in overall microbial community throughout the experiment. (B=bog, P=PSU and U=UAJA). Asterisks denote bands that exhibited comigration during analysis.
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fig6: DDGE gel from cycle 16 showing bands that were excised and identified. Gels were used in the PCA to monitor shifts in overall microbial community throughout the experiment. (B=bog, P=PSU and U=UAJA). Asterisks denote bands that exhibited comigration during analysis.

Mentions: Seven of the visually darkest bands in the DGGE gels during cycle 16 were excised and sequenced, assuming that these bands would represent the predominant species in the communities (Figure 6). None of the dark bands analyzed (bands 2, 3 and 4) showed sequence identity to Geobacter spp., which was shown to be dominant in the 16S rRNA gene clone library and pyrosequencing analysis. Analysis of additional bands (1 and 5) revealed the presence of bacteria that were most closely related to the known isolates Geobacter spp. (95% identity) and ‘Candidatus Protochlamydia sp.' (89%). Other bands sequenced were most closely related to the known Firmicutes isolates Clostridium sp. (89%) and Alkaliphilus sp. (89%), and the Gammaproteobacterium Pseudomonas sp. (99%) (Table 2). Cloning and sequencing of these prominent DGGE bands did not show evidence of DNA comigration. Other sequenced bands (6 and 7) did exhibit comigration, but did not include Geobacter.


Convergent development of anodic bacterial communities in microbial fuel cells.

Yates MD, Kiely PD, Call DF, Rismani-Yazdi H, Bibby K, Peccia J, Regan JM, Logan BE - ISME J (2012)

DDGE gel from cycle 16 showing bands that were excised and identified. Gels were used in the PCA to monitor shifts in overall microbial community throughout the experiment. (B=bog, P=PSU and U=UAJA). Asterisks denote bands that exhibited comigration during analysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475369&req=5

fig6: DDGE gel from cycle 16 showing bands that were excised and identified. Gels were used in the PCA to monitor shifts in overall microbial community throughout the experiment. (B=bog, P=PSU and U=UAJA). Asterisks denote bands that exhibited comigration during analysis.
Mentions: Seven of the visually darkest bands in the DGGE gels during cycle 16 were excised and sequenced, assuming that these bands would represent the predominant species in the communities (Figure 6). None of the dark bands analyzed (bands 2, 3 and 4) showed sequence identity to Geobacter spp., which was shown to be dominant in the 16S rRNA gene clone library and pyrosequencing analysis. Analysis of additional bands (1 and 5) revealed the presence of bacteria that were most closely related to the known isolates Geobacter spp. (95% identity) and ‘Candidatus Protochlamydia sp.' (89%). Other bands sequenced were most closely related to the known Firmicutes isolates Clostridium sp. (89%) and Alkaliphilus sp. (89%), and the Gammaproteobacterium Pseudomonas sp. (99%) (Table 2). Cloning and sequencing of these prominent DGGE bands did not show evidence of DNA comigration. Other sequenced bands (6 and 7) did exhibit comigration, but did not include Geobacter.

Bottom Line: After 16 cycles the predominance of Geobacter spp. in anode communities was identified using 16S rRNA gene clone libraries (58±10%), fluorescent in-situ hybridization (FISH) (63±6%) and pyrosequencing (81±4%).While the clone library analysis for the underperforming UAJA3 had a significantly lower percentage of Geobacter spp. sequences (36%), suggesting that a predominance of this microbe was needed for convergent power densities, the lower percentage of this species was not verified by FISH or pyrosequencing analyses.These results show that the predominance of Geobacter spp. in acetate-fed systems was consistent with good MFC performance and independent of the inoculum source.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, USA.

ABSTRACT
Microbial fuel cells (MFCs) are often inoculated from a single wastewater source. The extent that the inoculum affects community development or power production is unknown. The stable anodic microbial communities in MFCs were examined using three inocula: a wastewater treatment plant sample known to produce consistent power densities, a second wastewater treatment plant sample, and an anaerobic bog sediment. The bog-inoculated MFCs initially produced higher power densities than the wastewater-inoculated MFCs, but after 20 cycles all MFCs on average converged to similar voltages (470±20 mV) and maximum power densities (590±170 mW m(-2)). The power output from replicate bog-inoculated MFCs was not significantly different, but one wastewater-inoculated MFC (UAJA3 (UAJA, University Area Joint Authority Wastewater Treatment Plant)) produced substantially less power. Denaturing gradient gel electrophoresis profiling showed a stable exoelectrogenic biofilm community in all samples after 11 cycles. After 16 cycles the predominance of Geobacter spp. in anode communities was identified using 16S rRNA gene clone libraries (58±10%), fluorescent in-situ hybridization (FISH) (63±6%) and pyrosequencing (81±4%). While the clone library analysis for the underperforming UAJA3 had a significantly lower percentage of Geobacter spp. sequences (36%), suggesting that a predominance of this microbe was needed for convergent power densities, the lower percentage of this species was not verified by FISH or pyrosequencing analyses. These results show that the predominance of Geobacter spp. in acetate-fed systems was consistent with good MFC performance and independent of the inoculum source.

Show MeSH