Shaw Liz J, Nicol Graeme W, Smith Zena, Fear Jon, Prosser James I, Baggs Elizabeth M
Imperial College London, Wye Campus, Department of Agricultural Sciences, Wye, Kent, UK.
Environ Microbiol. 2006 Feb;8(2):214-22. doi: 10.1111/j.1462-2920.2005.00882.x.
Nitrous oxide (N(2)O) emission from soils is a major contributor to the atmospheric loading of this potent greenhouse gas. It is thought that autotrophic ammonia oxidizing bacteria (AOB) are a significant source of soil-derived N(2)O and a denitrification pathway (i.e. reduction of NO(2) (-) to NO and N(2)O), so-called nitrifier denitrification, has been demonstrated as a N(2)O production mechanism in Nitrosomonas europaea. It is thought that Nitrosospira spp. are the dominant AOB in soil, but little information is available on their ability to produce N(2)O or on the existence of a nitrifier denitrification pathway in this lineage. This study aims to characterize N(2)O production and nitrifier denitrification in seven strains of AOB representative of clusters 0, 2 and 3 in the cultured Nitrosospira lineage. Nitrosomonas europaea ATCC 19718 and ATCC 25978 were analysed for comparison. The aerobically incubated test strains produced significant (P < 0.001) amounts of N(2)O and total N(2)O production rates ranged from 2.0 amol cell(-1) h(-1), in Nitrosospira tenuis strain NV12, to 58.0 amol cell(-1) h(-1), in N. europaea ATCC 19718. Nitrosomonas europaea ATCC 19718 was atypical in that it produced four times more N(2)O than the next highest producing strain. All AOB tested were able to carry out nitrifier denitrification under aerobic conditions, as determined by production of (15)N-N(2)O from applied (15)N-NO(2) (-). Up to 13.5% of the N(2)O produced was derived from the exogenously applied (15)N-NO(2) (-). The results suggest that nitrifier denitrification could be a universal trait in the betaproteobacterial AOB and its potential ecological significance is discussed.
土壤中一氧化二氮（N₂O）的排放是这种强效温室气体大气负荷的主要贡献者。据认为，自养氨氧化细菌（AOB）是土壤源N₂O的重要来源，并且一种反硝化途径（即将NO₂⁻还原为NO和N₂O），即所谓的硝化细菌反硝化作用，已被证明是欧洲亚硝化单胞菌中N₂O的产生机制。据认为，亚硝化螺菌属是土壤中占主导地位的AOB，但关于它们产生N₂O的能力或该谱系中硝化细菌反硝化途径的存在情况，目前所知甚少。本研究旨在表征培养的亚硝化螺菌谱系中代表簇0、2和3的七株AOB的N₂O产生和硝化细菌反硝化作用。对欧洲亚硝化单胞菌ATCC 19718和ATCC 25978进行了分析以作比较。需氧培养的测试菌株产生了显著（P < 0.001）量的N₂O，总N₂O产生速率范围从细弱亚硝化螺菌菌株NV12的2.0 amol细胞⁻¹小时⁻¹到欧洲亚硝化单胞菌ATCC 19718的58.0 amol细胞⁻¹小时⁻¹。欧洲亚硝化单胞菌ATCC 19718是非典型的，因为它产生的N₂O比第二高产菌株多四倍。所有测试的AOB在需氧条件下都能够进行硝化细菌反硝化作用，这通过应用¹⁵N-NO₂⁻产生¹⁵N-N₂O来确定。产生的N₂O中高达13.5%源自外源应用的¹⁵N-NO₂⁻。结果表明，硝化细菌反硝化作用可能是β-变形菌纲AOB的一个普遍特征，并讨论了其潜在的生态意义。
