title: Nitrate-dependent ferrous iron oxidation by anaerobic ammonium oxidation (anammox) bacteria.
abstract: We examined nitrate-dependent Fe(2+) oxidation mediated by anaerobic ammonium oxidation (anammox) bacteria. Enrichment cultures of "Candidatus Brocadia sinica" anaerobically oxidized Fe(2+) and reduced NO3(-) to nitrogen gas at rates of 3.7 ± 0.2 and 1.3 ± 0.1 (mean ± standard deviation [SD]) nmol mg protein(-1) min(-1), respectively (37°C and pH 7.3). This nitrate reduction rate is an order of magnitude lower than the anammox activity of "Ca. Brocadia sinica" (10 to 75 nmol NH4(+) mg protein(-1) min(-1)). A (15)N tracer experiment demonstrated that coupling of nitrate-dependent Fe(2+) oxidation and the anammox reaction was responsible for producing nitrogen gas from NO3(-) by "Ca. Brocadia sinica." The activities of nitrate-dependent Fe(2+) oxidation were dependent on temperature and pH, and the highest activities were seen at temperatures of 30 to 45°C and pHs ranging from 5.9 to 9.8. The mean half-saturation constant for NO3(-) ± SD of "Ca. Brocadia sinica" was determined to be 51 ± 21 μM. Nitrate-dependent Fe(2+) oxidation was further demonstrated by another anammox bacterium, "Candidatus Scalindua sp.," whose rates of Fe(2+) oxidation and NO3(-) reduction were 4.7 ± 0.59 and 1.45 ± 0.05 nmol mg protein(-1) min(-1), respectively (20°C and pH 7.3). Co-occurrence of nitrate-dependent Fe(2+) oxidation and the anammox reaction decreased the molar ratios of consumed NO2(-) to consumed NH4(+) (ΔNO2(-)/ΔNH4(+)) and produced NO3(-) to consumed NH4(+) (ΔNO3(-)/ΔNH4(+)). These reactions are preferable to the application of anammox processes for wastewater treatment.
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Oshiki
authors.forename: S
authors.initials: S
authors.lastname: Ishii
authors.forename: K
authors.initials: K
authors.lastname: Yoshida
authors.forename: N
authors.initials: N
authors.lastname: Fujii
authors.forename: M
authors.initials: M
authors.lastname: Ishiguro
authors.forename: H
authors.initials: H
authors.lastname: Satoh
authors.forename: S
authors.initials: S
authors.lastname: Okabe
mesh_terms: D001421:Bacteria, Anaerobic / Q000235:genetics / Q000378:metabolism*; D019149:Bioreactors; D005296:Ferrous Compounds / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D017404:In Situ Hybridization, Fluorescence; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013696:Temperature
chemical_list: D005296:Ferrous Compounds; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D012336:RNA, Ribosomal, 16S