title: Propionate oxidation by and methanol inhibition of anaerobic ammonium-oxidizing bacteria.
abstract: 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 min(-1) mg of protein(-1)) 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 CO(2), 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.
authors.affiliation: Department of Microbiology, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands.
authors.forename: Didem
authors.initials: D
authors.lastname: Güven
authors.forename: Ana
authors.initials: A
authors.lastname: Dapena
authors.forename: Boran
authors.initials: B
authors.lastname: Kartal
authors.forename: Markus C
authors.initials: MC
authors.lastname: Schmid
authors.forename: Bart
authors.initials: B
authors.lastname: Maas
authors.forename: Katinka
authors.initials: K
authors.lastname: van de Pas-Schoonen
authors.forename: Seval
authors.initials: S
authors.lastname: Sozen
authors.forename: Ramon
authors.initials: R
authors.lastname: Mendez
authors.forename: Huub J M
authors.initials: HJ
authors.lastname: Op den Camp
authors.forename: Mike S M
authors.initials: MS
authors.lastname: Jetten
authors.forename: Marc
authors.initials: M
authors.lastname: Strous
authors.forename: Ingo
authors.initials: I
authors.lastname: Schmidt
mesh_terms: D001421:Bacteria, Anaerobic / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D003470:Culture Media; D000431:Ethanol / Q000494:pharmacology; D000432:Methanol / Q000494:pharmacology*; D010084:Oxidation-Reduction; D011422:Propionates / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*
chemical_list: D003470:Culture Media; D011422:Propionates; D000644:Quaternary Ammonium Compounds; D000431:Ethanol; D000432:Methanol