Mo Yongliang, Qi Xing-E, Li Aorui, Zhang Xinfang, Jia Zhongjun
College of Environmental Science and Engineering, China West Normal University, Nanchong, China.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China.
Front Microbiol. 2020 Nov 12;11:580866. doi: 10.3389/fmicb.2020.580866. eCollection 2020.
Methanotrophs are the only biofilters for reducing the flux of global methane (CH) emissions in water-logged wetlands. However, adaptation of aerobic methanotrophs to low concentrations of oxygen and nitrogen in typical swamps, such as that of the Qinghai-Tibetan Plateau, is poorly understood. In this study, we show that like methanotrophs dominate methane oxidation and nitrogen fixation under suboxic conditions in alpine swamp soils. Following incubation with C-CH and N-N for 90 days under suboxic conditions with repeated flushing using an inert gas (i.e., argon), microbial carbon and nitrogen turnover was measured in swamp soils at different depths: 0-20 cm (top), 40-60 cm (intermediate), and 60-80 cm (deep). Results show detectable methane oxidation and nitrogen fixation in all three soil depths. In particular, labeled carbon was found in CO enrichment (C-CO), and soil organic carbon (C-SOC), whereas labeled nitrogen (N) was detected in soil organic nitrogen (SON). The highest values of labeled isotopes were found at intermediate soil depths. High-throughput amplicon sequencing and Sanger sequencing indicated the dominance of -like methanotrophs in swamp soils, which comprised 21.3-24.0% of the total bacterial sequences, as measured by C-DNA at day 90. These results demonstrate that aerobic methanotroph is the key player in suboxic methane oxidation and likely catalyzes nitrogen fixation in swamp wetland soils in the Qinghai-Tibetan Plateau.
甲烷氧化菌是减少水涝湿地全球甲烷（CH）排放通量的唯一生物过滤器。然而，需氧甲烷氧化菌如何适应典型沼泽（如青藏高原的沼泽）中低浓度的氧气和氮气，目前还知之甚少。在本研究中，我们发现，在高寒沼泽土壤的缺氧条件下，类似甲烷氧化菌在甲烷氧化和固氮过程中占主导地位。在缺氧条件下，用惰性气体（即氩气）反复冲洗，将土壤与C-CH和N-N一起培养90天，然后测量不同深度（0-20厘米（表层）、40-60厘米（中层）和60-80厘米（深层））沼泽土壤中的微生物碳和氮周转情况。结果表明，在所有三个土壤深度都检测到了甲烷氧化和固氮现象。特别是，在CO富集物（C-CO）和土壤有机碳（C-SOC）中发现了标记碳，而在土壤有机氮（SON）中检测到了标记氮。标记同位素的最高值出现在土壤中层深度。高通量扩增子测序和桑格测序表明，类似甲烷氧化菌在沼泽土壤中占主导地位，在第90天通过C-DNA测量，其占细菌总序列的21.3-24.0%。这些结果表明，需氧甲烷氧化菌是缺氧甲烷氧化的关键参与者，可能在青藏高原沼泽湿地土壤中催化固氮作用。
