Journal
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
Volume 79, Issue 13, Pages 4087-4093Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/AEM.00743-13
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Funding
- New Energy and Industrial Technology Development Organization, Japan
- Steel Foundation for Environmental Protection Technology, Japan
- Japan Science and Technology Agency, CREST
- Japan Society for the Promotion of Science
- Grants-in-Aid for Scientific Research [11J04128] Funding Source: KAKEN
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We examined nitrate-dependent Fe2+ oxidation mediated by anaerobic ammonium oxidation (anammox) bacteria. Enrichment cultures of Candidatus Brocadia sinica anaerobically oxidized Fe2+ 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 degrees 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 N-15 tracer experiment demonstrated that coupling of nitrate-dependent Fe2+ oxidation and the anammox reaction was responsible for producing nitrogen gas from NO3- by Ca. Brocadia sinica. The activities of nitrate-dependent Fe2+ oxidation were dependent on temperature and pH, and the highest activities were seen at temperatures of 30 to 45 degrees 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 mu M. Nitrate-dependent Fe2+ oxidation was further demonstrated by another anammox bacterium, Candidatus Scalindua sp., whose rates of Fe2+ oxidation and NO3- reduction were 4.7 +/- 0.59 and 1.45 +/- 0.05 nmol mg protein(-1) min(-1), respectively (20 degrees C and pH 7.3). Co-occurrence of nitrate-dependent Fe2+ oxidation and the anammox reaction decreased the molar ratios of consumed NO2- to consumed NH4+ (Delta NO2-/Delta NH4+) and produced NO3- to consumed NH4+ (Delta NO3-/Delta NH4+). These reactions are preferable to the application of anammox processes for wastewater treatment.
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