Deiglmayr Kathrin, Philippot Laurent, Hartwig Ueli A, Kandeler Ellen
Institute of Crop Production and Grassland Research, University of Hohenheim, D-70593 Stuttgart, Germany.
FEMS Microbiol Ecol. 2004 Sep 1;49(3):445-54. doi: 10.1016/j.femsec.2004.04.017.
Rhizosphere soil was sampled in monocultures of Lolium perenne and Trifolium repens in June and October 2002, at two different nitrogen fertilisation levels (14 and 56 g N m(-2) year(-1)) and under two pCO(2) atmospheres (360 and 600 ppmv) at the Swiss FACE (Free Air Carbon dioxide Enrichment) site. Directly extracted soil DNA was analysed with restriction fragment length polymorphism (PCR-RFLP) by use of degenerated primers for the narG gene encoding the active site of the membrane-bound nitrate reductase. The corresponding enzyme activity of the nitrate reductase was determined colorimetrically after 24 h of anaerobic incubation. The narG PCR-RFLP fingerprints showed that the structure of the nitrate-reducing community was primarily affected by season and pH of the sampling site, whereas CO(2) enrichment, plant species or fertiliser treatment had no apparent effect. In contrast, the nitrate reductase activity responded to N fertilisation, CO(2) enrichment and plant species in October, whereas in June drought stress most likely kept the enzyme activity at a low level in all treatments. Apparently, the respiratory nitrate-reducing community adapted to different treatments primarily by altered enzyme activity.
2002年6月和10月，在瑞士自由空气二氧化碳浓度增加（FACE）试验点，于两种不同施氮水平（14和56克氮每平方米每年）及两种pCO₂大气浓度（360和600 ppmv）条件下，采集了多年生黑麦草和白三叶草单作时的根际土壤。利用针对编码膜结合硝酸还原酶活性位点的narG基因的简并引物，通过限制性片段长度多态性分析（PCR-RFLP）对直接提取的土壤DNA进行分析。在厌氧培养24小时后，比色法测定硝酸还原酶的相应酶活性。narG PCR-RFLP指纹图谱表明，硝酸盐还原菌群的结构主要受采样季节和采样点pH值的影响，而二氧化碳浓度升高、植物种类或施肥处理没有明显影响。相比之下，硝酸还原酶活性在10月对施氮、二氧化碳浓度升高和植物种类有响应，而在6月，干旱胁迫很可能使所有处理中的酶活性都维持在较低水平。显然，呼吸性硝酸盐还原菌群主要通过改变酶活性来适应不同处理。
