Department of Food Science and Technology, Chair of Microbiology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
FEMS Microbiol Ecol. 2012 Apr;80(1):114-23. doi: 10.1111/j.1574-6941.2011.01275.x. Epub 2012 Jan 9.
Ammonia oxidation, the first step in nitrification, is performed by autotrophic bacteria and thaumarchaea, whose relative contributions vary in different soils. Distinctive environmental niches for the two groups have not been identified, but evidence from previous studies suggests that activity of thaumarchaea, unlike that of bacterial ammonia oxidizers, is unaffected by addition of inorganic N fertilizer and that they preferentially utilize ammonia generated from the mineralization of organic N. This hypothesis was tested by determining the influence of both inorganic and organic N sources on nitrification rate and ammonia oxidizer growth and community structure in microcosms containing acidic, forest soil in which ammonia oxidation was dominated by thaumarchaea. Nitrification rate was unaffected by the incubation of soil with inorganic ammonium but was significantly stimulated by the addition of organic N. Oxidation of ammonia generated from native soil organic matter or added organic N, but not added inorganic N, was accompanied by increases in abundance of the thaumarchaeal amoA gene, a functional gene for ammonia oxidation, but changes in community structure were not observed. Bacterial amoA genes could not be detected. Ammonia oxidation was completely inhibited by 0.01% acetylene in all treatments, indicating ammonia monooxygenase-dependent activity. The findings have implications for current models of soil nitrification and for nitrification control strategies to minimize fertilizer loss and nitrous oxide production.
氨氧化作用，硝化作用的第一步，是由自养细菌和奇古菌完成的，它们的相对贡献在不同的土壤中有所不同。两组之间没有明显的独特环境小生境，但来自先前研究的证据表明，与细菌氨氧化菌不同，奇古菌的活性不受无机 N 肥料的添加影响，而且它们优先利用有机 N 矿化产生的氨。通过在含有酸性森林土壤的微宇宙中确定无机和有机 N 源对硝化速率以及氨氧化菌生长和群落结构的影响来检验这一假设，在这些微宇宙中，氨氧化作用主要由奇古菌主导。土壤中添加无机铵不会影响硝化作用，但添加有机 N 会显著刺激硝化作用。来自本地土壤有机质或添加的有机 N 的氨的氧化伴随着氨氧化功能基因（amoA 基因）的丰度增加，但没有观察到群落结构的变化。细菌 amoA 基因无法检测到。在所有处理中，0.01%的乙炔完全抑制了氨氧化作用，表明这是氨单加氧酶依赖的活性。这些发现对当前的土壤硝化模型和最小化肥料损失和一氧化二氮产生的硝化控制策略具有重要意义。
