添加碳源对不同pH水稻土中反硝化关键功能基因的影响

水稻是我国第一大粮食作物，稻田特有的淹水环境为反硝化作用的发生提供了必要条件，而反硝化作用造成的氮素平均利用率低、温室气体排放等问题日趋严重.反硝化作用作为微生物驱动的生物学过程，自身受到多种因素的影响.为揭示pH、有机碳源等关键限制因子对水稻土反硝化菌的影响，本研究以两种初始pH不同的碱性和酸性水稻土作为研究对象，通过室内泥浆厌氧培养试验，分别基于DNA和RNA水平分析了反硝化关键功能基因(nirK/S、nosZ)丰度变化规律，以期揭示外源添加有机碳源(葡萄糖)对不同pH水稻土中反硝化微生物功能活性及潜势的影响.结果表明：1)外源添加葡萄糖会降低土壤pH,且pH降低程度随添加葡萄糖浓度的增加而增加；2)碱性水稻土中添加葡萄糖增强了反硝化作用；酸性水稻土中添加葡萄糖对反硝化作用的影响不显著；3)不同pH水稻土中nirK和nirS的基因数量和表达量对添加葡萄糖的响应具有显著差异，其中nirK基因的响应程度相对更高；4)在酸性水稻土中，nosZ基因的数量和表达量随碳源浓度的升高而降低，而碱性水稻土添加低浓度葡萄糖后，碳源的刺激作用占主导地位，nosZ基因的数量和表达量均有所增加，添加高浓度...

Effects of carbon source addition on the key functional genes of denitrification in paddy soils with different pH

Rice is the largest grain crop in China,and its unique flooded paddy soil provides necessary condition for the occurrence of denitrification.However,the problems of nitrogen utilization decline and greenhouse gas emissions caused by denitrification have gained increasing concern.As a biological process driven by microorganisms,denitrification is affected by many factors such as soil pH and organic carbon sources.To reveal the effect of exogenous organic carbon on the functional activity and potential of denitrifying microorganisms in paddy soils with different pH values,this study added glucose to two paddy soils with different initial pH values and analyzed the abundance of key functional genes (nirK/S,nosZ) for denitrification at DNA and RNA levels.The results showed that the glucose reduced soil pH,the degree of which rose with the increase of the glucose concentration.The added glucose also enhanced soil denitrification,which was observed only in alkaline paddy soil.The responses of number and expression of nirK and nirS genes to glucose addition were significantly different between the two soils with different pH values,and the response degree of nirK gene was relatively higher.In acidic paddy soil,the number and expression of nosZ gene decreased with the increase of carbon source concentration;while in alkaline paddy soil,low concentration glucose significantly stimulated the number and expression of nosZ gene,but high concentration glucose caused soil acidification,which then inhibited the number and expression of nosZ gene.This study shows that exogenous organic carbon source affects the function and activity of denitrifying microorganisms in paddy soil from aspects of carbon source supply and soil acidification,which in turn influences the occurrence of denitrification and subsequent nitrous oxide emission.