Jetten M S, Strous M, van de Pas-Schoonen K T, Schalk J, van Dongen U G, van de Graaf A A, Logemann S, Muyzer G, van Loosdrecht M C, Kuenen J G
Kluyver Institute for Biotechnology, TU Delft, The Netherlands.
FEMS Microbiol Rev. 1998 Dec;22(5):421-37. doi: 10.1111/j.1574-6976.1998.tb00379.x.
From recent research it has become clear that at least two different possibilities for anaerobic ammonium oxidation exist in nature. 'Aerobic' ammonium oxidizers like Nitrosomonas eutropha were observed to reduce nitrite or nitrogen dioxide with hydroxylamine or ammonium as electron donor under anoxic conditions. The maximum rate for anaerobic ammonium oxidation was about 2 nmol NH4+ min-1 (mg protein)-1 using nitrogen dioxide as electron acceptor. This reaction, which may involve NO as an intermediate, is thought to generate energy sufficient for survival under anoxic conditions, but not for growth. A novel obligately anaerobic ammonium oxidation (Anammox) process was recently discovered in a denitrifying pilot plant reactor. From this system, a highly enriched microbial community with one dominating peculiar autotrophic organism was obtained. With nitrite as electron acceptor a maximum specific oxidation rate of 55 nmol NH4+ min-1 (mg protein)-1 was determined. Although this reaction is 25-fold faster than in Nitrosomonas, it allowed growth at a rate of only 0.003 h-1 (doubling time 11 days). 15N labeling studies showed that hydroxylamine and hydrazine were important intermediates in this new process. A novel type of hydroxylamine oxidoreductase containing an unusual P468 cytochrome has been purified from the Anammox culture. Microsensor studies have shown that at the oxic/anoxic interface of many ecosystems nitrite and ammonia occur in the absence of oxygen. In addition, the number of reports on unaccounted high nitrogen losses in wastewater treatment is gradually increasing, indicating that anaerobic ammonium oxidation may be more widespread than previously assumed. The recently developed nitrification systems in which oxidation of nitrite to nitrate is prevented form an ideal partner for the Anammox process. The combination of these partial nitrification and Anammox processes remains a challenge for future application in the removal of ammonium from wastewater with high ammonium concentrations.
近期研究表明，自然界中至少存在两种不同的厌氧氨氧化可能性。人们观察到，像嗜中性亚硝化单胞菌这样的“好氧”氨氧化菌在缺氧条件下，能以羟胺或铵作为电子供体来还原亚硝酸盐或二氧化氮。以二氧化氮作为电子受体时，厌氧氨氧化的最大速率约为2 nmol NH4+ min-1（mg蛋白质）-1。该反应可能以一氧化氮作为中间体，据认为能产生足够的能量以在缺氧条件下存活，但不足以支持生长。最近在一个反硝化中试工厂反应器中发现了一种新型的专性厌氧氨氧化（Anammox）过程。从这个系统中，获得了一个高度富集的微生物群落，其中有一种占主导地位的特殊自养生物。以亚硝酸盐作为电子受体时，测定的最大比氧化速率为55 nmol NH4+ min-1（mg蛋白质）-1。尽管该反应比在亚硝化单胞菌中的反应快25倍，但生长速率仅为0.003 h-1（倍增时间为11天）。15N标记研究表明，羟胺和肼是这个新过程中的重要中间体。已从Anammox培养物中纯化出一种含有异常P468细胞色素的新型羟胺氧化还原酶。微传感器研究表明，在许多生态系统的有氧/缺氧界面处，亚硝酸盐和氨在无氧的情况下出现。此外，关于废水处理中未解释的高氮损失的报道数量正在逐渐增加，这表明厌氧氨氧化可能比以前认为的更为普遍。最近开发的防止亚硝酸盐氧化为硝酸盐的硝化系统是Anammox过程的理想伙伴。这些部分硝化和Anammox过程的组合对于未来在去除高铵浓度废水中的铵的应用而言仍然是一个挑战。
