Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA.
ISME J. 2010 Jul;4(7):933-44. doi: 10.1038/ismej.2010.10. Epub 2010 Mar 11.
Ammonia oxidation is a central process in the nitrogen cycle. Particularly in marine and estuarine environments, few experiments have been conducted to tease apart the factors influencing their abundance and composition. To investigate the effect of nitrogen and phosphorus availability on ammonia-oxidizing bacteria (AOB), we conducted a nutrient enrichment experiment in a Maine salt marsh and sampled sediment communities in three seasons over 2 years. We assessed community composition using terminal restriction fragment length polymorphism analysis and sequencing of cloned fragments of the ammonia monooxygenase (amoA) gene. Almost all of the amoA sequences fell within the marine and estuarine-specific Nitrosospira-like clade. Applied separately, nitrogen and phosphorus significantly altered AOB composition; however, together the nutrients had an interactive effect, and composition did not change. In contrast, nutrient enrichment did not alter AOB abundance. Furthermore, the response of AOB composition to nutrient enrichment varied over time. We conclude that closely related taxa within the marine/estuarine-specific Nitrosospira-like clade vary in their preference for nutrient concentrations, and this preference may depend on other temporally variable abiotic factors. Finally, AOB composition was highly variable within and across years even in untreated plots. Further studies are needed to test how these different aspects of compositional variability in AOB communities influence nitrogen cycling.
氨氧化作用是氮循环中的一个核心过程。特别是在海洋和河口环境中，很少有实验能够分离出影响其丰度和组成的因素。为了研究氮和磷供应对氨氧化细菌（AOB）的影响，我们在缅因州盐沼进行了养分添加实验，并在两年的三个季节中对沉积物群落进行了采样。我们使用末端限制性片段长度多态性分析和克隆氨单加氧酶（amoA）基因片段的测序来评估群落组成。几乎所有的 amoA 序列都属于海洋和河口特异性的硝化螺旋菌（Nitrosospira-like）类群。氮和磷单独添加时显著改变了 AOB 的组成；然而，两者共同作用时有交互效应，组成并没有改变。相比之下，养分添加并没有改变 AOB 的丰度。此外，AOB 组成对养分添加的响应随时间而变化。我们的结论是，海洋/河口特异性硝化螺旋菌（Nitrosospira-like）类群中密切相关的分类单元在对营养浓度的偏好上存在差异，这种偏好可能取决于其他随时间变化的非生物因素。最后，即使在未处理的样点中，AOB 组成在年内和年际间也具有高度的可变性。需要进一步的研究来测试 AOB 群落组成的这些不同方面的可变性如何影响氮循环。
