Dissolved organic matter stimulates N2 fixation and nifH gene expression in Trichodesmium
Dissolved organic matter stimulates N2 fixation and nifH gene expression in Trichodesmium
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DOI：
10.1093/femsle/fnaa034
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发表时间：
2020-02-01
影响因子：
2.1
通讯作者：
Bonnet, Sophie
中科院分区：
文献类型：
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作者：
Benavides, Mar;Duhamel, Solange;Bonnet, Sophie
混合营养是异养和自养营养模式的结合，在海洋光合浮游生物中正逐渐成为一种规则而不是例外。束毛藻（Trichodesmium）是广泛存在于亚热带海洋中的一种重要的固氮生物，通常被认为是通过自养获得能量的。虽然束毛藻在缺乏无机磷源时利用溶解的有机磷的能力是众所周知的，但这种重要的蓝细菌在多大程度上可以从其他溶解的有机物（DOM）资源中受益是未知的。在这里，我们提供的证据，碳，氮，磷丰富的DOM分子提高N，固定率和nifH基因表达的天然束毛藻殖民地收集在热带南太平洋西部的两个站。在位于贫营养的南太平洋环流的第三站采样显示没有束毛藻，但显示存在UCYN-B，虽然没有检测到nifH表达。我们的研究结果表明，Trichodesmium的行为mixotrophically在一定的环境条件下，为他们提供代谢可塑性，并增加了认为，mixotrophic是广泛存在于海洋微生物。
Mixotrophy, the combination of heterotrophic and autotrophic nutrition modes, is emerging as the rule rather than the exception in marine photosynthetic plankton. Trichodesmium, a prominent diazotroph ubiquitous in the (sub)tropical oceans, is generally considered to obtain energy via autotrophy. While the ability of Trichodesmium to use dissolved organic phosphorus when deprived of inorganic phosphorus sources is well known, the extent to which this important cyanobacterium may benefit from other dissolved organic matter (DOM) resources is unknown. Here we provide evidence of carbon-, nitrogen- and phosphorus-rich DOM molecules enhancing N, fixation rates and nifH gene expression in natural Trichodesmium colonies collected at two stations in the western tropical South Pacific. Sampling at a third station located in the oligotrophic South Pacific Gyre revealed no Trichodesmium but showed presence of UCYN-B, although no nifH expression was detected. Our results suggest that Trichodesmium behaves mixotrophically in response to certain environmental conditions, providing them with metabolic plasticity and adding up to the view that mixotrophy is widespread among marine microbes.