Distribution and survival strategies of diazotrophs in the Arctic Ocean revealed by global-scale metagenomic analysis
Distribution and survival strategies of diazotrophs in the Arctic Ocean revealed by global-scale metagenomic analysis
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DOI：
10.1101/2022.10.28.514325
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
T. Shiozaki;Y. Nishimura;Susumu Yoshizawa;H. Takami;K. Hamasaki;A. Fujiwara;S. Nishino;N. Harada
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文献类型：
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作者：
T. Shiozaki;Y. Nishimura;Susumu Yoshizawa;H. Takami;K. Hamasaki;A. Fujiwara;S. Nishino;N. Harada
氮固定是海洋中活性氮的主要来源，被认为特别发生在低纬度贫营养海洋中。最近的研究表明，固氮作用也发生在极地地区，因此是一个全球性过程，尽管极地固氮生物的生理和生态特征尚不清楚。在这里，我们成功地重建了基因组，包括蓝藻UCYN-A（Atelocyanobacterium thalassa），从对应于111个样品分离自北冰洋的宏基因组数据。这些固氮生物在北冰洋非常丰富（最大，1.28%），表明它们在北极生态系统和生态地球化学循环中具有重要作用。北冰洋的固氮生物既有北极特有种，也有泛生种。北极特有的固氮生物，包括北极UCYN-A，具有独特的基因组（例如，芳烃降解）和/或非常小的细胞尺寸（<0.2 µm），表明适应北极特定条件。通用固氮生物通常是异养生物，通常具有编码冷诱导RNA伴侣的基因，这可能使它们即使在寒冷的沃茨和极地也能生存。因此，这两种类型的固氮生物具有适应其环境的生理特性，这使得固氮在全球范围内。
Nitrogen fixation is the major source of reactive nitrogen in the ocean and has been considered to occur specifically in low-latitude oligotrophic oceans. Recent studies have shown that nitrogen fixation also occurs in the polar regions and thus is a global process, although the physiological and ecological characteristics of polar diazotrophs are not yet known. Here, we successfully reconstructed genomes, including that of cyanobacterium UCYN-A (Candidatus ‘Atelocyanobacterium thalassa’), from metagenome data corresponding to 111 samples isolated from the Arctic Ocean. These diazotrophs were highly abundant in the Arctic Ocean (max., 1.28% of the total microbial community), suggesting that they have important roles in the Arctic ecosystem and biogeochemical cycles. Diazotrophs in the Arctic Ocean were either Arctic-specific or universal species. Arctic-specific diazotrophs, including Arctic UCYN-A, had unique gene sets (e.g., aromatics degradation) and/or a very small cell size (<0.2 µm), suggesting adaptations to Arctic-specific conditions. Universal diazotrophs were generally heterotrophs and commonly had the gene that encodes the cold-inducible RNA chaperone, which presumably makes their survival possible even in deep, cold waters and polar regions. Thus both types of diazotroph have physiological traits adaptable to their environments, which allow nitrogen fixation on a global scale.