脲酶抑制剂对土壤胞外-胞内脲酶活性关系、微生物脲酶基因特性的影响及机理

Urea is a widely used N fertilizer in China, accounting for more than half of total N fertilizers consumption. Urea applied to soils is usually hydrolazed rapidly to ammonium under the catalazed by soil extracellular urease, results in urea-N losses and environmental pollutions. Urease inhibitors could suppress the extracellular urease activity and retard the urea hydrolysis in soil. However, how the intracellular urease respond to the inhabitation of extracellular urease activity？If the microbial urease encoding genes (ureCgenes) which related to intracellular urease expression would change with the variation of intracellular urease? These remain poorly understood..Pre-incubated red, brown and cinnamon soils with different pH and organic matter are treated with urease inhibitors NBPT and PPT, respectively. Treated soils are incubated in a incubator at 25 degree. At 1, 3, 7, 14, 21, 28 days soils are sampled to study the change in soil extracellular urease activity, the variation of soil intracellular urease, and the characteristics of bacterial, fungal and archaeal ureCgenes. The aims of this study are: (1) to evaluate the inhabitation of soil extracellular urease activity under NBPT and PPD applications; (2) to assess the response of soil intracellular urease to suppressed soil extracellular urease activity; (3) to clarify that relationships between bacterial, fungal and archaeal ureCgenes to soil intracellular urease activity.

尿素是我国应用最广泛的氮肥品种。由于尿素施入土壤后在胞外脲酶的作用下水解很快，导致大量的氮素损失和严重的环境污染。国内外研究证明脲酶抑制剂可有效抑制胞外脲酶活性、延缓尿素水解过程。但在土壤胞外脲酶受抑时，胞外脲酶最重要的来源--胞内脲酶会否应激响应、与胞内脲酶活性表达有关的脲酶编码基因特性有否改变，将是国际研究的前沿热点。本项目以低、高有机质含量的不同pH值红壤、棕壤、褐土为供试土壤，以脲酶抑制剂NBPT和PPD为供试对象，研究其在6种供试土壤施用后土壤胞外脲酶活性的变化，以探明脲酶抑制剂对不同pH、不同有机质含量土壤中尿素水解过程的作用差异；研究胞外脲酶受抑制时胞内脲酶活性的变化，以阐明二者的应激关系；研究脲酶抑制剂使用条件下细菌、真菌、古菌ureCgene的变化特征，以揭示胞内-胞外脲酶应激关系的机理。在上述研究的基础上，为有效调控土壤尿素氮转化、提高其肥效并减少环境污染提供理论依据。

尿素是我国应用最广泛的氮肥品种,由于尿素施入土壤后在胞外脲酶的作用下水解很快，导致大量的氮素损失和严重的环境污染。国内外研究证明脲酶抑制剂可有效抑制胞外脲酶活性、延缓尿素水解过程。但在土壤胞外脲酶受抑时，胞外脲酶最重要的来源--胞内脲酶会否应激响应、与胞内脲酶活性表达有关的脲酶编码基因特性有否改变,目前尚缺乏相关研究。本研究以不同pH值的红壤、棕壤、褐土为供试土壤，以脲酶抑制剂NBPT和PPD为供试对象，首次揭示了当土壤胞外脲酶在施入脲酶抑制剂后活性受抑时，胞外脲酶最重要的来源--胞内脲酶的应激响应机制，并且发现了与胞内脲酶活性表达有关的脲酶编码基因的改变方式。研究发现在胞外脲酶受抑时，微生物为了满足自身潜在的氮素需求，会增殖制备脲酶并将其以储存在胞内。不同土壤中微生物在制备脲酶的过程中发挥的作用有差异，但是共同点是细菌相较真菌及古菌发挥着更加重要的作用。不同土壤上两种供试脲酶抑制剂对胞内外脲酶及微生物基因丰度的影响效果也存在着显著的差异，棕壤和褐土上NBPT的效果更好而红壤上则是PPD的效果更好，这可能是由于pH差异导致的。本研究将为有效调控土壤尿素氮转化、提高其肥效并减少环境污染提供理论依据。