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Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell.

Ishii S, Shimoyama T, Hotta Y, Watanabe K - BMC Microbiol. (2008)

Bottom Line: Fluorescence in-situ hybridization revealed that the Rhizobiales population represented rod-shaped cells with filamentous appendages and constituted over 30% of the total population.Bacteria affiliated with the Rhizobiales constituted the major population in the cellulose-fed MFC and exhibited unique morphology with filamentous appendages.They are considered to play important roles in the cellulose-degrading electrogenic community.

View Article: PubMed Central - HTML - PubMed

Affiliation: Marine Biotechnology Institute, Heita, Kamaishi, Iwate 026-000, Japan. shunichi-ishii@aist.go.jp

ABSTRACT

Background: Microbial fuel cells (MFCs) are devices that exploit microorganisms to generate electric power from organic matter. Despite the development of efficient MFC reactors, the microbiology of electricity generation remains to be sufficiently understood.

Results: A laboratory-scale two-chamber microbial fuel cell (MFC) was inoculated with rice paddy field soil and fed cellulose as the carbon and energy source. Electricity-generating microorganisms were enriched by subculturing biofilms that attached onto anode electrodes. An electric current of 0.2 mA was generated from the first enrichment culture, and ratios of the major metabolites (e.g., electric current, methane and acetate) became stable after the forth enrichment. In order to investigate the electrogenic microbial community in the anode biofilm, it was morphologically analyzed by electron microscopy, and community members were phylogenetically identified by 16S rRNA gene clone-library analyses. Electron microscopy revealed that filamentous cells and rod-shaped cells with prosthecae-like filamentous appendages were abundantly present in the biofilm. Filamentous cells and appendages were interconnected via thin filaments. The clone library analyses frequently detected phylotypes affiliated with Clostridiales, Chloroflexi, Rhizobiales and Methanobacterium. Fluorescence in-situ hybridization revealed that the Rhizobiales population represented rod-shaped cells with filamentous appendages and constituted over 30% of the total population.

Conclusion: Bacteria affiliated with the Rhizobiales constituted the major population in the cellulose-fed MFC and exhibited unique morphology with filamentous appendages. They are considered to play important roles in the cellulose-degrading electrogenic community.

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Magnified FE-SEM images for biofilms adhering onto graphite-fiber anodes. Anode biofilms enriched from the rice paddy field soil were shown in panels A and B, while Geobacter biofilms were shown in panels C and D. Bars are 500 nm.
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Figure 3: Magnified FE-SEM images for biofilms adhering onto graphite-fiber anodes. Anode biofilms enriched from the rice paddy field soil were shown in panels A and B, while Geobacter biofilms were shown in panels C and D. Bars are 500 nm.

Mentions: Electron micrographs revealed unique biofilm structures and cell shapes (Figs. 2 and 3). Photos show that biofilms were sparsely distributed on the graphite fibers (Fig. 3A) along with highly complicated structures comprised of morphologically different cells and cellulose fibers (Fig. 2B). Many rod-shaped cells had long filamentous appendages (approximately 100 nm in thickness) that, as seen at the edge of the biofilm (Figs. 2C), bridged between microbial cells and the electrodes. In other cases, cells themselves were filamentous and occasionally intertwined with each other (Fig. 2D). Rods with filamentous appendages seemed to be more abundant than filamentous cells.


Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell.

Ishii S, Shimoyama T, Hotta Y, Watanabe K - BMC Microbiol. (2008)

Magnified FE-SEM images for biofilms adhering onto graphite-fiber anodes. Anode biofilms enriched from the rice paddy field soil were shown in panels A and B, while Geobacter biofilms were shown in panels C and D. Bars are 500 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2254626&req=5

Figure 3: Magnified FE-SEM images for biofilms adhering onto graphite-fiber anodes. Anode biofilms enriched from the rice paddy field soil were shown in panels A and B, while Geobacter biofilms were shown in panels C and D. Bars are 500 nm.
Mentions: Electron micrographs revealed unique biofilm structures and cell shapes (Figs. 2 and 3). Photos show that biofilms were sparsely distributed on the graphite fibers (Fig. 3A) along with highly complicated structures comprised of morphologically different cells and cellulose fibers (Fig. 2B). Many rod-shaped cells had long filamentous appendages (approximately 100 nm in thickness) that, as seen at the edge of the biofilm (Figs. 2C), bridged between microbial cells and the electrodes. In other cases, cells themselves were filamentous and occasionally intertwined with each other (Fig. 2D). Rods with filamentous appendages seemed to be more abundant than filamentous cells.

Bottom Line: Fluorescence in-situ hybridization revealed that the Rhizobiales population represented rod-shaped cells with filamentous appendages and constituted over 30% of the total population.Bacteria affiliated with the Rhizobiales constituted the major population in the cellulose-fed MFC and exhibited unique morphology with filamentous appendages.They are considered to play important roles in the cellulose-degrading electrogenic community.

View Article: PubMed Central - HTML - PubMed

Affiliation: Marine Biotechnology Institute, Heita, Kamaishi, Iwate 026-000, Japan. shunichi-ishii@aist.go.jp

ABSTRACT

Background: Microbial fuel cells (MFCs) are devices that exploit microorganisms to generate electric power from organic matter. Despite the development of efficient MFC reactors, the microbiology of electricity generation remains to be sufficiently understood.

Results: A laboratory-scale two-chamber microbial fuel cell (MFC) was inoculated with rice paddy field soil and fed cellulose as the carbon and energy source. Electricity-generating microorganisms were enriched by subculturing biofilms that attached onto anode electrodes. An electric current of 0.2 mA was generated from the first enrichment culture, and ratios of the major metabolites (e.g., electric current, methane and acetate) became stable after the forth enrichment. In order to investigate the electrogenic microbial community in the anode biofilm, it was morphologically analyzed by electron microscopy, and community members were phylogenetically identified by 16S rRNA gene clone-library analyses. Electron microscopy revealed that filamentous cells and rod-shaped cells with prosthecae-like filamentous appendages were abundantly present in the biofilm. Filamentous cells and appendages were interconnected via thin filaments. The clone library analyses frequently detected phylotypes affiliated with Clostridiales, Chloroflexi, Rhizobiales and Methanobacterium. Fluorescence in-situ hybridization revealed that the Rhizobiales population represented rod-shaped cells with filamentous appendages and constituted over 30% of the total population.

Conclusion: Bacteria affiliated with the Rhizobiales constituted the major population in the cellulose-fed MFC and exhibited unique morphology with filamentous appendages. They are considered to play important roles in the cellulose-degrading electrogenic community.

Show MeSH