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Coupled nitrogen and oxygen isotope effects of anaerobic ammonium oxidation (anammox)
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| Title: | Coupled nitrogen and oxygen isotope effects of anaerobic ammonium oxidation (anammox) |
| Other Titles: | アナモックス細菌の窒素および酸素同位体分別の解析 |
| Authors: | 小林, 香苗1 Browse this author |
| Authors(alt): | Kobayashi, Kanae1 |
| Issue Date: | 25-Mar-2021 |
| Publisher: | Hokkaido University |
| Abstract: | Natural abundance of stable nitrogen (N) and oxygen (O) isotopes (δ15N and δ18O) are invaluable biogeochemical tracers for assessing the N transformations in the environment. To fully exploit these tracers, the N and O isotope effects (15ε and 18ε) associated with the respective N transformation processes must be known. Anaerobic ammonium oxidation (anammox) and denitrification are the two major sinks of fixed N. In addition, anammox bacteria contribute to re-oxidation of nitrite (NO2-) to nitrate (NO3-), because they fix CO2 into biomass with reducing equivalents generated from oxidation of NO2- to NO3-. NO3- production by anammox bacteria influences the NO2- and NO3- N and O isotope effects in freshwater and marine systems. Despite the significant importance of anammox bacteria in the global N cycle, 15ε and 18ε of anammox are not well known. Therefore, the never yet determined 15ε and 18ε associated with anammox were investigated in this study. Firstly, the 15ε were determined for ‘Ca. Scalindua sp.’, ‘Ca. Jettenia caeni’, and ‘Ca. Brocadia sinica’ growing in continuous enrichment cultures. All three anammox species yielded similar 15ε values of NH4+ oxidation to N2 (15εNH4→N2 = 30.9 ~ 32.7‰) and inverse kinetic isotope effects of NO2- oxidation to NO3- (15εNO2→NO3 = - 45.3‰ ~ - 30.1‰). In contrast, the values of NO2- reduction to N2 was significantly different among three species (15εNO2→N2 = 5.9 ~ 29.5‰), which is probably because individual anammox bacteria species might possess different types of nitrite reductase. Secondly, the 18ε were determined for ‘Ca. Scalindua sp.’, which is a putative marine species. Determination of 18ε of anammox is more challenging because the δ18ONO2 value is affected by abiotic O isotope exchange between NO2- and H2O (keq, 18εeq) and incorporation of a water-derived O atom into NO3- during NO2- oxidation to NO3- (18εH2O). In order to determine abiotic keq, 18εeq, and 18εH2O, batch experiments with different δ18OH2O values of medium were conducted. Oxygen isotope ratio measurements of NO2- and NO3- by the azide method and denitrifier method are sensitive to the δ18O of sample water. However, the influence of δ18OH2O on those measurements has not been quantitatively evaluated and documented so far. Therefore, the influence of δ18OH2O of sample on δ18O analysis of NO2- and NO3- were quantitatively evaluated. Then, the rate of abiotic O isotope exchange between NO2- and H2O: keq = 1.13 × 10-2 (h-1), as well as equilibrium isotope effects: 18εeq = 11.9‰ were experimentally determined. To determine 18ε of each reaction, batch culture experiments with different δ18OH2O values of medium (δ18OH2O = -12.6 ~ 110.1‰) were conducted for ‘Ca. Scalindua sp.’. A numerical model was developed for estimation of respective 18ε of anammox reaction, resulting in 18εNO2→N2 = 9.8 ~10.5‰, 18εNO2→NO3 = -3.3 ~ -1.9‰, and 18εH2O= 24.1 ~ 25.6‰, respectively. These 18ε values were determined for the first time in the world. These obtained dual N and O isotopic effects could provide significant insights into the contribution of anammox bacteria to the fixed N loss and NO2- reoxidation in (recycling N) in various natural environments. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第14449号 |
| Degree Level: | 博士 |
| Degree Discipline: | 工学 |
| Examination Committee Members: | (主査) 教授 岡部 聡, 教授 木村 克輝, 教授 佐藤 久, 准教授 押木 守 |
| Degree Affiliation: | 工学院（環境創生工学専攻） |
| (Relation)haspart: | Kobayashi, Kanae., Fukushima, Keitaro., Onishi, Yuji., Nishina, Kazuya., Makabe, Akiko., Yano, Midori., et al. (2020). Influence of δ18O of water on measurements of δ18O of nitrite and nitrate. Rapid Commun Mass Spectrom. 35, 2: e8979. | | Kobayashi, Kanae., Makabe, Akiko., Yano, Midori., Oshiki, Mamoru., Kindaichi, Tomonori., Casciotti, Karen.L., and Okabe, Satoshi. (2019). Dual nitrogen and oxygen isotope fractionation during anaerobic ammonium oxidation by anammox bacteria. 13: 2426-2436. |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/91540 |
| Appears in Collections: | 課程博士 (Doctorate by way of Advanced Course) > 工学院(Graduate School of Engineering)
学位論文 (Theses) > 博士 （工学）
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