Pessi Igor S, Viitamäki Sirja, Virkkala Anna-Maria, Eronen-Rasimus Eeva, Delmont Tom O, Marushchak Maija E, Luoto Miska, Hultman Jenni
Department of Microbiology, University of Helsinki, Viikinkaari 9, 00014, Helsinki, Finland.
Helsinki Institute of Sustainability Science (HELSUS), Yliopistonkatu 3, 00014, Helsinki, Finland.
Environ Microbiome. 2022 Jun 11;17(1):30. doi: 10.1186/s40793-022-00424-2.
In contrast to earlier assumptions, there is now mounting evidence for the role of tundra soils as important sources of the greenhouse gas nitrous oxide (NO). However, the microorganisms involved in the cycling of NO in this system remain largely uncharacterized. Since tundra soils are variable sources and sinks of NO, we aimed at investigating differences in community structure across different soil ecosystems in the tundra.
We analysed 1.4 Tb of metagenomic data from soils in northern Finland covering a range of ecosystems from dry upland soils to water-logged fens and obtained 796 manually binned and curated metagenome-assembled genomes (MAGs). We then searched for MAGs harbouring genes involved in denitrification, an important process driving NO emissions. Communities of potential denitrifiers were dominated by microorganisms with truncated denitrification pathways (i.e., lacking one or more denitrification genes) and differed across soil ecosystems. Upland soils showed a strong NO sink potential and were dominated by members of the Alphaproteobacteria such as Bradyrhizobium and Reyranella. Fens, which had in general net-zero NO fluxes, had a high abundance of poorly characterized taxa affiliated with the Chloroflexota lineage Ellin6529 and the Acidobacteriota subdivision Gp23.
By coupling an in-depth characterization of microbial communities with in situ measurements of NO fluxes, our results suggest that the observed spatial patterns of NO fluxes in the tundra are related to differences in the composition of denitrifier communities.
与早期的假设相反，现在有越来越多的证据表明冻原土壤是温室气体一氧化二氮（N₂O）的重要来源。然而，该系统中参与N₂O循环的微生物在很大程度上仍未得到充分表征。由于冻原土壤是N₂O的可变源和汇，我们旨在研究冻原不同土壤生态系统中群落结构的差异。
我们分析了来自芬兰北部土壤的1.4太字节宏基因组数据，这些土壤涵盖了从干旱高地土壤到水涝沼泽等一系列生态系统，并获得了796个经过人工分类和整理的宏基因组组装基因组（MAG）。然后，我们搜索了含有参与反硝化作用（驱动N₂O排放的一个重要过程）基因的MAG。潜在反硝化菌群落主要由具有截断反硝化途径（即缺少一个或多个反硝化基因）的微生物组成，并且在不同土壤生态系统中存在差异。高地土壤显示出很强的N₂O汇潜力，主要由变形菌门α亚纲的成员如慢生根瘤菌属和雷氏菌属主导。沼泽的N₂O通量总体上为净零，含有大量与绿弯菌门Ellin6529谱系和酸杆菌门Gp23亚类相关的未充分表征的分类群。
通过将微生物群落的深入表征与N₂O通量的原位测量相结合，我们的结果表明，冻原中观察到的N₂O通量空间模式与反硝化菌群落组成的差异有关。
