Gammaproteobacterial methanotrophs dominate methanotrophy in aerobic and anaerobic layers of boreal lake waters
Gammaproteobacterial methanotrophs dominate methanotrophy in aerobic and anaerobic layers of boreal lake waters
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DOI：
10.3354/ame01874
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发表时间：
2018-01-01
影响因子：
1.4
通讯作者：
Nykanen, Hannu
中科院分区：
文献类型：
--
作者：
Rissanen, Antti J.;Saarenheimo, Jatta;Nykanen, Hannu
北方地区的小型氧气分层腐殖湖泊是大气中甲烷的重要来源。虽然稳定同位素分析表明，甲烷的很大一部分已经在这些湖泊的厌氧水层中氧化，在这个过程中的好氧和厌氧甲烷氧化菌的贡献是未知的。我们使用mcrA和16 S rRNA基因的下一代测序来表征芬兰2个北方湖泊（Alinen-Mustajarvi湖和Mekkojarvi湖）水柱中的微生物群落，并通过Alinen-Mustajarvi的鸟枪宏基因组分析和Mekkojarvi的pmoA基因和16 S rRNA，mcrA和pmoA转录本分析对此进行了补充。此外，我们测试了各种电子受体和光对甲烷氧化（C-13-CH 4标记）的孵化从湖泊收集的水样的效果。好氧γ-变形菌甲烷氧化菌（甲基球菌目）完全占主导地位的甲烷氧化菌群落以上和以下的湖泊中的氧跃层。一个新的谱系内的Methylococcales，Alinensis，在这里第一次定义，占主导地位的Alinen-Mustajarvi，而甲烷氧化菌属于Methylobacter更丰富的Mekkojarvi。光照促进了缺氧水层中甲烷的氧化，而除NO3-外，其它电子受体（SO 42-、Fe 3+、Mn 4+和蒽醌-2，6-二磺酸盐）均抑制了甲烷的氧化.我们的研究结果表明，产氧光合作用可能燃料甲烷营养下的好氧水层在富含甲烷的北方湖泊。此外，孵育结果，以及从γ蛋白细菌甲烷氧化菌的宏基因组组装的基因组中检测到的反硝化基因，意味着北方湖泊甲烷氧化菌可能在缺氧条件下将甲烷氧化与NOx还原偶联。
Small oxygen-stratified humic lakes of the boreal zone are important sources of methane to the atmosphere. Although stable isotope profiling has indicated that a substantial part of methane is already oxidized in the anaerobic water layers in these lakes, the contributions of aerobic and anaerobic methanotrophs in the process are unknown. We used next-generation sequencing of mcrA and 16S rRNA genes to characterize the microbial communities in the water columns of 2 boreal lakes in Finland, Lake Alinen-Mustajarvi and Lake Mekkojarvi, and complemented this with a shotgun metagenomic analysis from Alinen-Mustajarvi and an analysis of pmoA genes and 16S rRNA, mcrA, and pmoA transcripts from Mekkojarvi. Furthermore, we tested the effect of various electron acceptors and light on methane oxidation (C-13-CH4 labeling) in incubations of water samples collected from the lakes. Aerobic gammaproteobacterial methanotrophs (order Methylococcales) exclusively dominated the methanotrophic community both above and below the oxycline in the lakes. A novel lineage within Methylococcales, Candidatus Methyloumidiphilus alinensis, defined here for the first time, dominated in Alinen-Mustajarvi, while methanotrophs belonging to Methylobacter were more abundant in Mekkojarvi. Light enhanced methane oxidation in the anoxic water layer, while alternative electron acceptors (SO42-, Fe3+, Mn4+, and anthraquinone-2, 6-disulfonate), except for NO3-, suppressed the process. Our results suggest that oxygenic photosynthesis potentially fuels methanotrophy below the aerobic water layers in methane-rich boreal lakes. Furthermore, incubation results, together with the detection of denitrification genes from metagenome-assembled genomes of gammaproteo-bacterial methanotrophs, imply that boreal lake methanotrophs may couple methane oxidation with NOx- reduction in hypoxic conditions.