|Alternative Title||Community structure and functional acitivity of ammonia-oxidizers in soils under different land uses|
|Place of Conferral||北京|
|Keyword||全程氨氧化，氨氧化细菌，氨氧化古菌，硝化螺菌， 13C稳定同位素标记 Comammox, AOB, AOA, Nitrospira, C stable isotope probing|
硝化作用是氮循环的重要环节，在土壤生态系统中广泛存在。硝化作用不仅直接影响着植物对氮素的利用效率，还与土壤酸化、温室气体 N2O产生、硝酸盐淋失造成水体污染等密切相关。一百多年来，硝化作用被认为是由氨氧化过程（NH3转变为 NO2−-N）和亚硝化过程（NO2−-N氧化成 NO−3 -N）两个反应步骤组成，其中氨氧化过程由氨氧化细菌（AOB）和氨氧化古菌（AOA）催化完成；亚硝化过程由亚硝酸盐氧化细菌（NOB）催化完成，二者密切合作才能完成整个硝化过程。2015年，研究发现亚硝酸盐氧化菌中的一些硝化螺菌可将氨直接氧化为硝酸盐，即全程氨氧化（Comammox，complete ammonia oxidation）,Comammox的发现打破了我们对微生物驱动的硝化作用的传统认知。但目前有关 Comammox Nitrospira在土壤环境中的分布特征、功能活性及其与 AOA、AOB对土壤硝化作用的相对贡献还不清楚。
（3）对农田土壤（pH5.80），过渡带土壤（pH6.07）和自然林土壤（pH4.99）进行13CO2稳定同位素标记研究结果表明，农田土壤中硝化作用比过渡带和自然林土壤活跃。在 30天的培养过程中，农田土壤中 AOA，AOB和 Comammox Nitrospira clade B的丰度显著上升；过渡带土壤中仅 AOA的丰度显著上升；自然林土壤中 Comammox Nitrospira的 clade A和 clade B均显著上升。对 13/12CO2标记的DNA样品进行超高速离心分离和分析发现，农田和过渡带土壤中AOA可通过化能自养作用同化13CO2到其DNA中，而 AOB和 Comammox Nitrospira 没有检测到，表明 AOA为酸性土壤中活跃的氨氧化微生物类群，农田土壤中这些活性的 AOA主要为 Nitrososphaera（91.9%）, Nitrosopumilus（3.6%）和Nitrosotalea（4.5%）三个簇，而过渡带土壤中活跃的 AOA主要为 Nitrososphaera簇。
Nitrification is an important component of the global nitrogen (N) cycle and widely takes place in soil ecosystems. Nitrification could directly affect the efficiency of plants in nitrogen utilization, and is closely related to soil acidification, N2O emissions and water pollution through nitrate leaching. For more than 100 years,nitrification was recognized as a two-step process including oxidation of ammonia to nitrite catalyzed by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), and oxidation of nitrite to nitrate by nitrite-oxidizing bacteria (NOB),and could only be completed by the cooperation between ammonia-oxidizers and NOB. At the year of 2015, this long-held concept was challenged by the discovery of Comammox (Complete ammonia oxidation) Nitrospira, being capable of oxidizing ammonia to nitrate in a single organism. However, the distribution and the functional activity of Comammox Nitrospira and the different contributions of Comammox Nitrospira, AOA and AOB to nitrification were still rarely known in soils.In this study, soil samples under diffent land uses, including cropland, grassland, bushland, forest land and transition land between bushland and forest land were collected. Quantitative PCR, clone library, DNA-SIP and clone library sequencing were employed to study the distribution pattern and functional activities of ammonia-oxidizers，including AOA, AOB and Comammox Nitrospira. The obtained results were listed below.
(1) Significant differences in soil basic properties were observed in soils under different land uses. All five soils were acidic with pH ranging from 4.99 to 6.50; there were significant differences in the available nitrogen concentrations of the soils. Cropland and grassland soils had relatively higher concentrations of available nitrogen with mainly nitrate form than bushland, transition land and forest land with mainly ammonium form.
(2) Significant differences in the abundance of ammonia-oxidizers were found in soils under different land uses. The abundance relationship of ammonia-oxidizers in cropland is AOB > AOA > Comammox Nitrospira while that in other soils is Comammox Nitrospira > AOA > AOB. The highest abundance of AOA could be observed in transition land soils at 8.51×106 copies•g-1 dry soil while no significant difference in AOA abundance in other soils; the highest abundance of AOB could be observed in cropland soils at 1.2×107 copies•g-1 dry soil while no significant difference in AOA abundance in other soils; the highest abundance of Comammox
|贺子洋. 不同土地利用方式下土壤氨氧化微生物的群落组成和功能特征[D]. 北京. 中国科学院生态环境研究中心,2019.|
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