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Applied and Environmental Microbiology, February 2005, p. 1066-1071, Vol. 71, No. 2
0099-2240/05/$08.00+0 doi:10.1128/AEM.71.2.1066-1071.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Environmental Engineering, Faculty of Civil Engineering, Istanbul Technical University, Istanbul, Turkey,1 Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela, Santiago de Compostela, Galicia, Spain,2 Department of Microbiology, University of Nijmegen, Nijmegen,3 Department of Biotechnology, Technical University Delft, Delft, The Netherlands,4 Department of Microbiology, University of Bayreuth, Bayreuth, Germany5
Received 19 May 2004/ Accepted 27 September 2004
Anaerobic ammonium oxidation (anammox) is a recently discovered microbial pathway and a cost-effective way to remove ammonium from wastewater. Anammox bacteria have been described as obligate chemolithoautotrophs. However, many chemolithoautotrophs (i.e., nitrifiers) can use organic compounds as a supplementary carbon source. In this study, the effect of organic compounds on anammox bacteria was investigated. It was shown that alcohols inhibited anammox bacteria, while organic acids were converted by them. Methanol was the most potent inhibitor, leading to complete and irreversible loss of activity at concentrations as low as 0.5 mM. Of the organic acids acetate and propionate, propionate was consumed at a higher rate (0.8 nmol min1 mg of protein1) by Percoll-purified anammox cells. Glucose, formate, and alanine had no effect on the anammox process. It was shown that propionate was oxidized mainly to CO2, with nitrate and/or nitrite as the electron acceptor. The anammox bacteria carried out propionate oxidation simultaneously with anaerobic ammonium oxidation. In an anammox enrichment culture fed with propionate for 150 days, the relative amounts of anammox cells and denitrifiers did not change significantly over time, indicating that anammox bacteria could compete successfully with heterotrophic denitrifiers for propionate. In conclusion, this study shows that anammox bacteria have a more versatile metabolism than previously assumed.
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