Ward B B
Department of Geosciences, Princeton University, Princeton, New Jersey, USA.
Methods Enzymol. 2011;486:307-23. doi: 10.1016/B978-0-12-381294-0.00013-4.
Nitrification is the process that converts ammonium to nitrate and thus links the regeneration of organic nitrogen to fixed nitrogen loss by denitrification. The first step, oxidation of ammonia to nitrite, is performed by a phylogenetically restricted group of proteobacteria (ammonia-oxidizing bacteria, AOB) and Crenarchaea (ammonia-oxidizing archaea, AOA). The second step is restricted to nitrite-oxidizing bacteria (NOB) as far as currently known. All three groups are assumed to be autotrophic and obligately aerobic, but the true extent of autotrophy and potential anaerobic pathways in these organisms is currently under investigation. Here, we describe methods for the measurement of nitrification rates in the marine environment, with a focus on seawater systems and stable isotopic tracer methods. The methods vary in analytical requirements but share the need for incubations, which must be optimized for different environments with different substrate concentrations. Recent advances in mass spectrometry now make it possible to minimize incubation artifacts and to achieve greatly improved sensitivity.
硝化作用是将铵转化为硝酸盐的过程，从而将有机氮的再生与反硝化作用导致的固定氮损失联系起来。第一步，将氨氧化为亚硝酸盐，由一组系统发育受限的变形菌（氨氧化细菌，AOB）和泉古菌（氨氧化古菌，AOA）进行。第二步，就目前所知，仅限于亚硝酸盐氧化细菌（NOB）。据推测，所有这三类微生物都是自养型且专性需氧的，但这些生物中自养的真实程度和潜在的厌氧途径目前正在研究中。在此，我们描述了测量海洋环境中硝化速率的方法，重点是海水系统和稳定同位素示踪方法。这些方法在分析要求上有所不同，但都需要进行培养，且必须针对不同底物浓度的不同环境进行优化。质谱技术的最新进展现在使得将培养假象降至最低并实现灵敏度的大幅提高成为可能。
