Characterization of bacterial and archaeal communities in air-cathode microbial fuel cells, open circuit and sealed-off reactors
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A large percentage of organic fuel consumed in a microbial fuel cell (MFC) is lost as a result of oxygen transfer through the cathode. In order to understand how this oxygen transfer affects the microbial community structure, reactors were operated in duplicate using three configurations: closed circuit (CC; with current generation), open circuit (OC; no current generation), and sealed off cathodes (SO; no current, with a solid plate placed across the cathode). Most (98 %) of the chemical oxygen demand (COD) was removed during power production in the CC reactor (maximum of 640 ± 10 mW/m2), with a low percent of substrate converted to current (coulombic efficiency of 26.5 ± 2.1 %). Sealing the cathode reduced COD removal to 7 %, but with an open cathode, there was nearly as much COD removal by the OC reactor (94.5 %) as the CC reactor. Oxygen transfer into the reactor substantially affected the composition of the microbial communities. Based on analysis of the biofilms using 16S rRNA gene pyrosequencing, microbes most similar to Geobacter were predominant on the anodes in the CC MFC (72 % of sequences), but the most abundant bacteria were Azoarcus (42 to 47 %) in the OC reactor, and Dechloromonas (17 %) in the SO reactor. Hydrogenotrophic methanogens were most predominant, with sequences most similar to Methanobacterium in the CC and SO reactor, and Methanocorpusculum in the OC reactors. These results show that oxygen leakage through the cathode substantially alters the bacterial anode communities, and that hydrogenotrophic methanogens predominate despite high concentrations of acetate. The predominant methanogens in the CC reactor most closely resembled those in the SO reactor, demonstrating that oxygen leakage alters methanogenic as well as general bacterial communities.
KeywordsAir-cathode Microbial community Oxygen intrusion 16S rRNA gene pyrosequencing
This work was sponsored by a PhD fellowship, a Global Research Partnership-Collaborative Fellows award (GRP-CF-2011-14-S), KAUST Award KUS–I1–003–13 (Bruce E. Logan) and discretionary investigator funds (Pascal E. Saikaly) at King Abdullah University of Science and Technology (KAUST). Special thanks are extended to Hari Ananda Rao for PCR assistance and Mohammed Alarawi and Dr. Shahjahan Ali of the Bioscience Core Laboratory at KAUST for 454 pyrosequencing.
- Caporaso JG, Kuczynski J, Stombaugh J, Bittinger K, Bushman FD, Costello EK, Fierer N, Pena AG, Goodrich JK, Gordon JI, Huttley GA, Kelley ST, Knights D, Koenig JE, Ley RE, Lozupone CA, McDonald D, Muegge BD, Pirrung M, Reeder J, Sevinsky JR, Turnbaugh PJ, Walters WA, Widmann J, Yatsunenko T, Zaneveld J, Knight R (2010b) QIIME allows analysis of high-throughput community sequencing data. Nat Methods 7(5):335–336PubMedCrossRefGoogle Scholar
- Cord-Ruwisch R, Lovley DR, Schink B (1998) Growth of Geobacter sulfurreducens with acetate in syntrophic cooperation with hydrogen-oxidizing anaerobic partners. Appl Environ Microb 64(6):2232–2236Google Scholar
- Daims H, Wagner M (2010) Microbial ecology of activated sludge. Robert Seviour and Per Halkjaer Nielsen (eds). IWA Publishing, London, pp. 259–280Google Scholar
- Gorby YA, Yanina S, McLean JS, Rosso KM, Moyles D, Dohnalkova A, Beveridge TJ, Chang IS, Kim BH, Kim KS, Culley DE, Reed SB, Romine MF, Saffarini DA, Hill EA, Shi L, Elias DA, Kennedy DW, Pinchuk G, Watanabe K, Ishii S, Logan B, Nealson KH, Fredrickson JK (2006) Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms. P Natl Acad Sci USA 103(30):11358–11363CrossRefGoogle Scholar
- Mechichi T, Stackebrandt E, Gad'on N, Fuchs G (2002) Phylogenetic and metabolic diversity of bacteria degrading aromatic compounds under denitrifying conditions, and description of Thauera phenylacetica sp. nov., Thauera aminoaromatica sp. nov., and Azoarcus buckelii sp. nov. Arch Microbiol 178(1):26–35PubMedCrossRefGoogle Scholar
- Rittmann BE, McCarty PL (2001) Environmental biotechnology: principles and applications. McGraw-Hill, New YorkGoogle Scholar