Martin-Jézéquel Véronique, Calu Guillaume, Candela Leo, Amzil Zouher, Jauffrais Thierry, Séchet Véronique, Weigel Pierre
FR CNRS-Université de Nantes-Ifremer 3473, EA 2160, Pôle Mer et Littoral, 2 rue de la Houssinière, BP 92208, 44322 Nantes Cédex 3, France.
CNRS UMR 7266, LIENSs, Université La Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle, France.
Mar Drugs. 2015 Nov 26;13(12):7067-86. doi: 10.3390/md13127055.
Over the last century, human activities have altered the global nitrogen cycle, and anthropogenic inputs of both inorganic and organic nitrogen species have increased around the world, causing significant changes to the functioning of aquatic ecosystems. The increasing frequency of Pseudo-nitzschia spp. in estuarine and coastal waters reinforces the need to understand better the environmental control of its growth and domoic acid (DA) production. Here, we document Pseudo-nitzschia spp. growth and toxicity on a large set of inorganic and organic nitrogen (nitrate, ammonium, urea, glutamate, glutamine, arginine and taurine). Our study focused on two species isolated from European coastal waters: P. multiseries CCL70 and P. australis PNC1. The nitrogen sources induced broad differences between the two species with respect to growth rate, biomass and cellular DA, but no specific variation could be attributed to any of the inorganic or organic nitrogen substrates. Enrichment with ammonium resulted in an enhanced growth rate and cell yield, whereas glutamate did not support the growth of P. multiseries. Arginine, glutamine and taurine enabled good growth of P. australis, but without toxin production. The highest DA content was produced when P. multiseries grew with urea and P. australis grew with glutamate. For both species, growth rate was not correlated with DA content but more toxin was produced when the nitrogen source could not sustain a high biomass. A significant negative correlation was found between cell biomass and DA content in P. australis. This study shows that Pseudo-nitzschia can readily utilize organic nitrogen in the form of amino acids, and confirms that both inorganic and organic nitrogen affect growth and DA production. Our results contribute to our understanding of the ecophysiology of Pseudo-nitzschia spp. and may help to predict toxic events in the natural environment.
在过去的一个世纪里，人类活动改变了全球氮循环，世界各地无机和有机氮物种的人为输入都有所增加，导致水生生态系统的功能发生了显著变化。河口和沿海水域中拟菱形藻属物种的出现频率不断增加，这进一步凸显了更深入了解其生长及软骨藻酸（DA）产生的环境控制因素的必要性。在此，我们记录了拟菱形藻属物种在大量无机和有机氮（硝酸盐、铵、尿素、谷氨酸、谷氨酰胺、精氨酸和牛磺酸）上的生长和毒性情况。我们的研究聚焦于从欧洲沿海水域分离出的两个物种：多列拟菱形藻CCL70和南方拟菱形藻PNC1。氮源在生长速率、生物量和细胞DA方面导致了这两个物种之间存在广泛差异，但无法将任何特定变化归因于任何一种无机或有机氮底物。铵的添加导致生长速率和细胞产量提高，而谷氨酸不能支持多列拟菱形藻的生长。精氨酸、谷氨酰胺和牛磺酸能使南方拟菱形藻良好生长，但不产生毒素。当多列拟菱形藻以尿素为氮源生长且南方拟菱形藻以谷氨酸为氮源生长时，产生的DA含量最高。对于这两个物种，生长速率与DA含量均无相关性，但当氮源无法维持高生物量时会产生更多毒素。在南方拟菱形藻中，细胞生物量与DA含量之间存在显著的负相关。本研究表明，拟菱形藻能够轻易利用氨基酸形式的有机氮，并证实无机和有机氮都会影响生长和DA的产生。我们的结果有助于我们理解拟菱形藻属物种的生态生理学，并可能有助于预测自然环境中的有毒事件。
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