Centre for Marine Ecosystems Research, School of Science, Edith Cowan University, Joondalup, WA, Australia.
Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Crawley, WA, Australia.
ISME J. 2018 Nov;12(11):2796-2800. doi: 10.1038/s41396-018-0218-6. Epub 2018 Jul 5.
Microorganisms play a critical role in nitrogen cycling by mineralising dissolved organic nitrogen (DON) compounds into bioavailable inorganic forms (DIN). Although DIN is crucial for seagrass growth, the hypothesis that seagrass leaf associated-microorganisms could convert DON to forms available for plant uptake has never been tested. We conducted a laboratory-based experiment in which seagrass (Posidonia sinuosa) leaves were incubated with N-amino acids (aa), with and without associated microorganisms. Samples were collected after 0.5, 2, 6 and 12 h. Both bulk stable isotope and nanoscale secondary ion mass spectrometry (NanoSIMS) analysis showed high accumulation of N within seagrass leaf tissues with an associated microbiota, but not in plants devoid of microorganisms. These results significantly change our understanding of the mechanisms of seagrass nitrogen use and provide evidence that seagrass microbiota increase nitrogen availability for uptake by seagrass leaves by mineralising aa, thus enhancing growth and productivity of these important coastal ecosystems.
微生物通过将溶解有机氮（DON）化合物矿化为生物可利用的无机形式（DIN）来在氮循环中发挥关键作用。尽管 DIN 对海草的生长至关重要，但微生物可以将 DON 转化为植物可吸收的形式这一假说从未得到过验证。我们进行了一项基于实验室的实验，在该实验中，用 N-氨基酸（aa）孵育海草（波西多尼亚海草）叶片，有和没有相关微生物。在 0.5、2、6 和 12 小时后收集样品。批量稳定同位素和纳米二次离子质谱（NanoSIMS）分析均显示，具有相关微生物的海草叶片组织内 N 的积累量很高，但在没有微生物的植物中则不然。这些结果极大地改变了我们对海草氮利用机制的理解，并提供了证据表明，海草微生物通过矿化 aa 增加了氮的可利用性，从而提高了这些重要沿海生态系统中海草叶片的吸收能力，进而提高了它们的生长和生产力。
