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

<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Results</p> <p>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 <it>Clostridiales</it>, <it>Chloroflexi</it>, <it>Rhizobiales </it>and <it>Methanobacterium</it>. Fluorescence in-situ hybridization revealed that the <it>Rhizobiales </it>population represented rod-shaped cells with filamentous appendages and constituted over 30% of the total population.</p> <p>Conclusion</p> <p>Bacteria affiliated with the <it>Rhizobiales </it>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.</p

Vilinska ljubav i licemjerje svijeta. Jean Giraudoux, Ondine, 56. dubrovačke ljetne igre

<p><b>Copyright information:</b></p><p>Taken from "Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell"</p><p>http://www.biomedcentral.com/1471-2180/8/6</p><p>BMC Microbiology 2008;8():6-6.</p><p>Published online 10 Jan 2008</p><p>PMCID:PMC2254626.</p><p></p>he anode chamber (mM); closed diamond, propionate in the anode chamber (mM); open triangle, methane in the anode chamber. Methane concentration was expressed as 'mM equivalent (eq.)' by supposing that all methane was present in the aqueous phase. Broken lines represent times when the anode electrode was transferred to new anode chambers, solid stars indicate times when cellulose (6 g l) was added to the anode chambers, while arrows indicate times when pH in the anode chamber was adjusted to 7.0. The arrowhead indicates the time when the cathode chamber was supplemented with potassium ferricyanide

Simulating the Contribution of Coaggregation to Interspecies Hydrogen Fluxes in Syntrophic Methanogenic Consortia

A simple model (termed the syntrophy model) for simulating the contribution of coaggregation to interspecies hydrogen fluxes between syntrophic bacteria and methanogenic archaea is described. We applied it to analyzing partially aggregated syntrophic cocultures with various substrates, revealing that large fractions of hydrogen molecules were fluxed in aggregates

Coaggregation Facilitates Interspecies Hydrogen Transfer between Pelotomaculum thermopropionicum and Methanothermobacter thermautotrophicus

A thermophilic syntrophic bacterium, Pelotomaculum thermopropionicum strain SI, was grown in a monoculture or coculture with a hydrogenotrophic methanogen, Methanothermobacter thermautotrophicus strain ΔH. Microscopic observation revealed that cells of each organism were dispersed in a monoculture independent of the growth substrate. In a coculture, however, these organisms coaggregated to different degrees depending on the substrate; namely, a large fraction of the cells coaggregated when they were grown on propionate, but relatively few cells coaggregated when they were grown on ethanol or 1-propanol. Field emission-scanning electron microscopy revealed that flagellum-like filaments of SI cells played a role in making contact with ΔH cells. Microscopic observation of aggregates also showed that extracellular polymeric substance-like structures were present in intercellular spaces. In order to evaluate the importance of coaggregation for syntrophic propionate oxidation, allowable average distances between SI and ΔH cells for accomplishing efficient interspecies hydrogen transfer were calculated by using Fick's diffusion law. The allowable distance for syntrophic propionate oxidation was estimated to be approximately 2 μm, while the allowable distances for ethanol and propanol oxidation were 16 μm and 32 μm, respectively. Considering that the mean cell-to-cell distance in the randomly dispersed culture was approximately 30 μm (at a concentration in the mid-exponential growth phase of the coculture of 5 × 10(7) cells ml(−1)), it is obvious that close physical contact of these organisms by coaggregation is indispensable for efficient syntrophic propionate oxidation

Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell-0

<p><b>Copyright information:</b></p><p>Taken from "Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell"</p><p>http://www.biomedcentral.com/1471-2180/8/6</p><p>BMC Microbiology 2008;8():6-6.</p><p>Published online 10 Jan 2008</p><p>PMCID:PMC2254626.</p><p></p>he anode chamber (mM); closed diamond, propionate in the anode chamber (mM); open triangle, methane in the anode chamber. Methane concentration was expressed as 'mM equivalent (eq.)' by supposing that all methane was present in the aqueous phase. Broken lines represent times when the anode electrode was transferred to new anode chambers, solid stars indicate times when cellulose (6 g l) was added to the anode chambers, while arrows indicate times when pH in the anode chamber was adjusted to 7.0. The arrowhead indicates the time when the cathode chamber was supplemented with potassium ferricyanide

Rarefaction curves for the different phylotypes obtained from the 16S rRNA gene clone libraries for the original rice paddy field soil and the anode biofilms

<p><b>Copyright information:</b></p><p>Taken from "Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell"</p><p>http://www.biomedcentral.com/1471-2180/8/6</p><p>BMC Microbiology 2008;8():6-6.</p><p>Published online 10 Jan 2008</p><p>PMCID:PMC2254626.</p><p></p

Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell-5

<p><b>Copyright information:</b></p><p>Taken from "Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell"</p><p>http://www.biomedcentral.com/1471-2180/8/6</p><p>BMC Microbiology 2008;8():6-6.</p><p>Published online 10 Jan 2008</p><p>PMCID:PMC2254626.</p><p></p>he anode chamber (mM); closed diamond, propionate in the anode chamber (mM); open triangle, methane in the anode chamber. Methane concentration was expressed as 'mM equivalent (eq.)' by supposing that all methane was present in the aqueous phase. Broken lines represent times when the anode electrode was transferred to new anode chambers, solid stars indicate times when cellulose (6 g l) was added to the anode chambers, while arrows indicate times when pH in the anode chamber was adjusted to 7.0. The arrowhead indicates the time when the cathode chamber was supplemented with potassium ferricyanide