Autotrophic ammonia-oxidizing bacteria contribute minimally to nitrification in a nitrogen-impacted forested ecosystem
Autotrophic ammonia-oxidizing bacteria contribute minimally to nitrification in a nitrogen-impacted forested ecosystem
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DOI：
10.1128/aem.71.1.197-206.2005
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发表时间：
2005-01-01
影响因子：
4.4
通讯作者：
Stein, LY
中科院分区：
文献类型：
--
作者：
Jordan, FL;Cantera, JJL;Stein, LY
在加利福尼亚州洛杉矶以东的圣贝纳迪诺山脉，大气含氮污染物向森林的沉积率是北美报告的最高水平。来自山脉西端的酸性土壤是氮饱和的，具有更高的氮矿化、硝化和硝酸盐淋溶速率。我们通过调查自养氨氧化群落的组成、丰度和活性来评估这种沉重的氮负荷对自养氨氧化群落的影响。对177个克隆的β-变形杆菌氨氧化剂16S rRNA基因的分析表明，在高度和中等氮素影响的土壤中，物种组成水平相似；所有土壤都支持先前特征的亚硝酸菌簇2、3和4。定量聚合酶链式反应测定的氨氧化剂丰度在不同土壤中也是相似的。然而，氮饱和土壤的潜在硝化活性速率高于从受影响较小的地点采集的土壤，但自养(即，乙炔敏感)活性在所有被检查的土壤中都很低。氮素饱和土壤培养30天后，土壤中的氨氮积累了额外的可溶性铵，而氮素影响较小的土壤则净损失了铵。最后，尽管保持了最佳的氨氧化条件，但在pH控制的氨改良灭菌土壤浆液中，培养的适应较高氨浓度的自养型氨氧化细菌多形亚硝酸菌的亚硝酸盐产生受到显著抑制。综上所述，这些结果表明，除自养氨氧化菌以外的其他因素导致了这些受氮影响的森林土壤的高硝化速率，而且与许多其他环境不同的是，氮含量和土壤pH的差异不利于特定的自养氨氧化菌类。
Deposition rates of atmospheric nitrogenous pollutants to forests in the San Bernardino Mountains range east of Los Angeles, California, are the highest reported in North America. Acidic soils from the west end of the range are N-saturated and have elevated rates of N-mineralization, nitrification, and nitrate leaching. We assessed the impact of this heavy nitrogen load on autotrophic ammonia-oxidizing communities by investigating their composition, abundance, and activity. Analysis of 177 cloned beta-Proteobacteria ammonia oxidizer 16S rRNA genes from highly to moderately N-impacted soils revealed similar levels of species composition; all of the soils supported the previously characterized Nitrosospira clusters 2, 3, and 4. Ammonia oxidizer abundance measured by quantitative PCR was also similar among the soils. However, rates of potential nitrification activity were greater for N-saturated soils than for soils collected from a less impacted site, but autotrophic (i.e., acetylene-sensitive) activity was low in all soils examined. N-saturated soils incubated for 30 days with ammonium accumulated additional soluble ammonium, whereas less-N-impacted soils had a net loss of ammonium. Lastly, nitrite production by cultivated Nitrosospira multiformis, an autotrophic ammonia-oxidizing bacterium adapted to relatively high ammonium concentrations, was significantly inhibited in pH-controlled slurries of sterilized soils amended with ammonium despite the maintenance of optimal ammonia-oxidizing conditions. Together, these results showed that factors other than autotrophic ammonia oxidizers contributed to high nitrification rates in these N-impacted forest soils and, unlike many other environments, differences in nitrogen content and soil pH did not favor particular autotrophic ammonia oxidizer groups.