Methanogens are crucial to global methane budget and carbon cycling. Methanogens from the phylum Euryarchaeota are currently classified into one class and seven orders, including two novel methanogen taxa, Methanofastidiosa and Methanomassiliicoccales. The relative importance of the novel methanogens to methane production in the natural environment is poorly understood. Here, we used a combined metagenomic and metatranscriptomic approach to investigate the metabolic activity of methanogens in mangrove sediments in Futian Nature Reserve, Shenzhen. We obtained 13 metagenome-assembled genomes (MAGs) representing one class (Methanofastidiosa) and five orders (Methanomassiliicoccales, Methanomicrobiales, Methanobacteriales, Methanocellales, and Methanosarcinales) of methanogens, including the two novel methanogens. Comprehensive annotation indicated the presence of an H2–dependent methylotrophic methanogenesis pathway in Methanofastidiosa and Methanomassiliicoccales. Based on the functional gene analysis, hydrogenotrophic and methylotrophic methanogenesis are the dominant pathways in mangrove sediments. MAG mapping revealed that hydrogenotrophic Methanomicrobiales were the most abundant methanogens and that methylotrophic Methanomassiliicoccales were the most active methanogens in the analyzed sediment profile, suggesting their important roles in methane production. Partial or near-complete genomes of two novel methanogen taxa, Methanofastidiosa and Methanomassiliicoccales, in natural environments were recovered and analyzed here for the first time. The presented findings highlight the ecological importance of the two novel methanogens and complement knowledge of how methane is produced in mangrove ecosystem. This study implies that two novel methanogens play a vital role in carbon cycle.

中文翻译：

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从红树林沉积物中发现新型产甲烷菌的产甲烷潜力的基因组和转录组学见解。

产甲烷菌对于全球甲烷预算和碳循环至关重要。Euryarchaeota门的产甲烷菌目前分为一类和七个等级，包括两个新颖的产甲烷菌类群，即Methanofastidiosa和Methanomassiliicoccales。新型产甲烷菌对自然环境中甲烷生产的相对重要性了解甚少。在这里，我们使用了宏基因组学和超转录组学相结合的方法来研究深圳福田自然保护区红树林沉积物中产甲烷菌的代谢活性。我们获得了13个由元基因组组装的基因组（MAGs），它们代表一类（包括两种新的产甲烷菌）产甲烷菌的一类（Methanofastidiosaosa）和五个顺序（Methanomassiliicoccales，Methanomicrobiales，Methanobacteriales，Methanocellales和Methanosarcinales）。全面的注释表明，在甲氧甲烷菌和甲烷菌中，存在依赖于H2的甲基营养型甲烷生成途径。根据功能基因分析，氢营养型和甲基营养型甲烷生成是红树林沉积物中的主要途径。MAG测绘表明，在分析的沉积物中，氢营养型甲烷微生物是最丰富的产甲烷菌，而甲基营养型甲烷甲烷菌是最活跃的产甲烷菌，表明它们在甲烷生产中的重要作用。首次在自然环境中回收并分析了两个新的产甲烷菌分类群（Methanofastidiosa和Methanomassiliicoccales）的部分或接近完整的基因组。提出的发现突出了这两种新型产甲烷菌的生态重要性，并补充了在红树林生态系统中如何产生甲烷的知识。这项研究表明，两种新型产甲烷菌在碳循环中起着至关重要的作用。