Mahmood Shahid, Prosser James I
School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, UK.
FEMS Microbiol Ecol. 2006 Jun;56(3):444-54. doi: 10.1111/j.1574-6941.2006.00070.x.
In grazed, grassland soils, sheep urine generates heterogeneity in ammonia concentrations, with potential impact on ammonia oxidizer community structure and soil N cycling. The influence of different levels of synthetic sheep urine on ammonia oxidizers was studied in grassland soil microcosms. 'Total' and active ammonia oxidizers were distinguished by comparing denaturing gradient gel electrophoresis (DGGE) profiles following PCR and RT-PCR amplification of 16S rRNA gene fragments, targeting DNA and RNA, respectively. The RNA-based approach indicated earlier, more reproducible and finer scale qualitative shifts in ammonia oxidizing communities than DNA-based analysis, but led to amplification of a small number of nonammonia oxidizer sequences. Qualitative changes in RNA-derived DGGE profiles were related to changes in nitrate accumulation. Sequence analysis of excised DGGE bands revealed that ammonia oxidizing communities in synthetic sheep urine-treated soils consisted mainly of Nitrosospira clusters 2, 3 and 4. Nitrosospira cluster 2 increased in relative abundance in microcosms treated with all levels of synthetic sheep urine. Low levels additionally led to increased relative abundance of Nitrosospira cluster 4 and medium and high levels increased relative abundance of cluster 3. Synthetic sheep urine is therefore likely to influence the spatial distribution and composition of ammonia oxidizer communities, with consequent effects on nitrate accumulation.
在放牧的草原土壤中，绵羊尿液会导致氨浓度出现异质性，这可能会对氨氧化菌群落结构和土壤氮循环产生影响。我们在草原土壤微观系统中研究了不同水平的合成绵羊尿液对氨氧化菌的影响。通过分别对靶向DNA和RNA的16S rRNA基因片段进行PCR和RT-PCR扩增后，比较变性梯度凝胶电泳（DGGE）图谱，区分了“总”氨氧化菌和活性氨氧化菌。基于RNA的方法显示，与基于DNA的分析相比，氨氧化菌群落的定性变化出现得更早、更具可重复性且规模更精细，但导致少量非氨氧化菌序列的扩增。RNA衍生的DGGE图谱中的定性变化与硝酸盐积累的变化有关。对切下的DGGE条带进行序列分析表明，合成绵羊尿液处理土壤中的氨氧化菌群落主要由亚硝化螺菌属簇2、3和4组成。在所有水平的合成绵羊尿液处理的微观系统中，亚硝化螺菌属簇2的相对丰度增加。低水平的合成绵羊尿液还导致亚硝化螺菌属簇4的相对丰度增加，中高水平则增加了簇3的相对丰度。因此，合成绵羊尿液可能会影响氨氧化菌群落的空间分布和组成，从而对硝酸盐积累产生影响。
