Response of symbiotic and asymbiotic nitrogen-fixing microorganisms to nitrogen fertilizer application
Response of symbiotic and asymbiotic nitrogen-fixing microorganisms to nitrogen fertilizer application
复制标题
共生和非共生固氮微生物对施氮肥的响应
DOI：
10.1007/s11368-018-2192-z
复制
发表时间：
2019-04-01
影响因子：
3.6
通讯作者：
Yao, Huaiying
中科院分区：
文献类型：
--
作者：
Li, Yaying;Pan, Fuxia;Yao, Huaiying
目的生物固氮（BNF）通过将大气中的氮素转移到土壤中，在氮素循环中发挥重要作用。生物固氮是由共生和非共生固氮微生物进行的。本研究采用15 N-N2和13 C-CO2标记、DNA稳定同位素探针（SIP）和分子生物学技术，对不同施氮水平下固氮菌的丰度、活性、群落结构以及根系分泌物对固氮菌的影响进行了研究。研究了不同氮肥水平下水稻土中共生固氮菌和非共生固氮菌的数量、活性和结构。低氮处理的根瘤中nifH基因丰度显著高于对照（零）和高氮处理。土壤中固氮菌数量丰富，生物多样性较高。SoilnifH基因序列主要由α-、β-和δ-变形菌以及蓝细菌组成。高氮条件下，α-变形菌相对丰度较低，蓝藻相对丰度较高。13 CO2培养和DNA-SIP分析结果表明，α-变形菌OTU 65在13 C标记土壤重组分中的丰度高于未标记土壤，表明α-变形菌可能对根际沉积碳的选择性高于其他有机碳。而δ-变形菌OTU 24和OTU 73在13 C标记和未标记样品中的轻组分丰度都相对较高，表明δ-变形菌可能更喜欢其他土壤有机碳而不是根沉积碳。适量施氮可提高紫云英共生生物固氮活性。根际豆科植物-根瘤菌系统的生物固氮活性是通过宿主植物与固氮菌之间的有机碳、氮养分交换来调节的。
PurposeBiological nitrogen fixation (BNF) plays an important role in nitrogen cycling by transferring atmospheric dinitrogen to the soil. BNF is performed by symbiotic and asymbiotic nitrogen-fixing microorganisms. However, the abundance, activity, and community structure of diazotrophs under different nitrogen fertilizer application rates and how root exudates influence diazotrophs remain unclear.Materials and methods15N-N2and13C-CO2labeling, DNA-based stable isotope probing (SIP), and molecular biological techniques were used in this study. The abundance, activity, and structure of symbiotic and asymbiotic diazotrophs under different nitrogen fertilizer applications in paddy soil were investigated.Results and discussionWe found that the nitrogen fixation capacity in milk vetch (Astragalus sinicusL.) andnifHgene abundance in the root nodules were significantly higher in the low-nitrogen treatment than in the control (zero) and high-nitrogen treatments. Nitrogen-fixing bacteria were abundant in the soils with a high biodiversity. SoilnifHgene sequences were dominated byα-,β-, andδ-proteobacteria, as well as byCyanobacteria. The relative abundance ofα-proteobacteriawas lower, and the relative abundance ofCyanobacteriawas higher under high nitrogen. Incubation of soil with13CO2and subsequent DNA-SIP analysis demonstrated that OTU65 fromα-proteobacteriawas relatively more abundant in heavy fractions of the13C-labeled soils than that in the unlabeled soils, indicating thatα-proteobacteriamay prefer rhizodeposition carbon to other organic carbon. However, OTU24 and OTU73 fromδ-proteobacteriahad relatively high abundances in light fractions both in the13C-labeled and unlabeled samples, indicating thatδ-proteobacteriamay prefer other soil organic carbon to rhizodeposition carbon.ConclusionsThe results suggested that soil N availability and rhizodeposition strongly modified the microbial communities of nitrogen-fixing bacteria. Moderate nitrogen application increased the symbiotic biological N fixing activity in theAstragalus sinicusL. rhizosphere. The BNF activity in the legume-rhizobia system is regulated by the exchange of organic C and N nutrient between the host plant and N-fixing bacteria.