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中國科學院南京土壤研究所研究員謝祖彬課題組利用自主研製的氣密植物生長箱,對水稻進行15N2氣體田間原位示蹤,以識別「活躍」固氮微生物。相關成果發表於Biology and Fertility of Soils(IF=5.521)。
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Abstract
The biological nitrogen fixation in planted and nonplanted paddy soils was quantified using a chamber-based 15N2-labeling technique, and the active diazotrophs of soil were assessed by 15N2-DNA-stable isotope probing (SIP). In addition, the nanometer scale secondary ion mass spectrometry (NanoSIMS) was applied to analysis the 15N-enrichment of soil DNA in SIP fractions. 15N2-labeling experiment showed that BNF was 11.33 ± 1.90 kg N ha1 in the rice-planted soil and 3.55 ± 1.18 kg N ha1 in the nonplanted soil after 28-day labeling. The biologically fixed 15N was mainly (> 95%) recovered in the surface layer (0–0.5 cm) in the rice-planted soil. High throughput sequencing of nifH genes extracted from surface soil showed that the presence of rice affected the community composition of diazotrophs. The relative abundance of Nostocales and Stigonematales was significantly higher in rice-planted soil than in nonplanted soil (P < 0.05). After CsCl gradient ultracentrifugation, NanoSIMS images clearly showed that 15N was incorporated into soil DNA in the 15N2-labeling SIP gradient fractions. Analyses of nifH genes in 15N-enriched SIP gradient fractions suggested that Nostocales and Stigonematales were the major contributors to BNF in the rice-soil system. Taken together, these results have highlighted the contributions of cyanobacteria to the BNF in paddy fields and improved our understanding of the close relationship between rice plants and cyanobacteria.

稻田生物固氮作用是稻田氮素循環的關鍵環節,而固氮微生物是驅動稻田生物固氮的引擎,因此,準確識別「活躍」固氮微生物,有利於提升稻田系統生物固氮潛力。中國科學院南京土壤研究所研究員謝祖彬課題組利用自主研製的氣密植物生長箱,對水稻進行15N2氣體田間原位示蹤。標記結束後,結合穩定同位素核酸探針技術(DNA-SIP)和納米二次離子質譜技術(NanoSIMS),可視化定量化分析超高速離心後不同密度梯度層內微生物DNA的15N豐度,為推導稻田土壤「活躍」固氮微生物提供直接證據。研究表明,與不種水稻土壤處理相比,水稻種植處理顯著提高生物固氮固定的氮素;基於nifH功能基因的高通量測序結果顯示,念珠藻目(Nostocales)和真枝藻目(Stigonematales)固氮微生物的相對豐度在種水稻處理中顯著提高;具有超高靈敏度的NanoSIMS能夠直接觀測納克級土壤DNA樣品的15N豐度。研究人員對不同密度梯度層次nifH基因測序,發現念珠藻目和真枝藻目藍細菌是該稻田土壤生物固氮的主要貢獻者。
責任編輯:宋瀟
校對和審核:張陽 王農
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