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Physiological changes induced by sodium chloride stress in Aphanizomenon gracile, Cylindrospermopsis raciborskii and Dolichospermum sp.
Harmful Algae ( IF 6.6 ) Pub Date : 2021-04-08 , DOI: 10.1016/j.hal.2021.102028
Emilie Houliez , Enora Briand , Florent Malo , Georges-Augustin Rovillon , Fabienne Hervé , Elise Robert , Laetitia Marchand , Agata Zykwinska , Amandine M.N. Caruana

Due to anthropogenic activities, associated with climate change, many freshwater ecosystems are expected to experience an increase in salinity. This phenomenon is predicted to favor the development and expansion of freshwater cyanobacteria towards brackish waters due to their transfer along the estuarine freshwater-marine continuum. Since freshwater cyanobacteria are known to produce toxins, this represents a serious threat for animal and human health. Saxitoxins (STXs) are classified among the most powerful cyanotoxins. It becomes thus critical to evaluate the capacity of cyanobacteria producing STXs to face variations in salinity and to better understand the physiological consequences of sodium chloride (NaCl) exposure, in particular on their toxicity. Laboratory experiments were conducted on three filamentous cyanobacteria species isolated from brackish (Dolichospermum sp.) and fresh waters (Aphanizomenon gracile and Cylindrospermopsis raciborskii) to determine how salinity variations affect their growth, photosynthetic activity, pigment composition, production of reactive oxygen species (ROS), synthesis of compatible solutes and STXs intracellular quotas. Salinity tolerance was found to be species-specific. Dolichospermum sp. was more resistant to salinity variations than A. gracile and C. raciborskii. NaCl variations reduced growth in all species. In A. gracile, carotenoids content was dose-dependently reduced by NaCl. By contrast, in C. raciborskii and Dolichospermum sp., variations in carotenoids content did not show obvious relationships with NaCl concentration. While in Dolichospermum sp. phycocyanin and phycoerythrin increased within the first 24 h exposure to NaCl, in both A. gracile and C. raciborskii, these pigments decreased proportionally to NaCl concentration. Low changes in salinity did not impact STXs production in A. gracile and C. raciborskii while higher increase in salinity could modify the toxin profile and content of C. raciborskii (intracellular STX decreased while dc-GTX2 increased). In estuaries, A. gracile and C. raciborskii would not be able to survive beyond the oligohaline area (i.e. salinity > 5). Conversely, in part due to its ability to accumulate compatible solutes, Dolichospermum sp. has the potential to face consequent salinity variations and to survive in the polyhaline area (at least up to salinity = 24).



中文翻译:

氯化钠胁迫引起的Aphanizomenon gracile,Cylindrospermopsis raciborskiiDolichospermum sp。的生理变化。

由于与气候变化有关的人为活动,预计许多淡水生态系统的盐度会增加。由于这种现象沿河口淡水-海洋连续体的转移,预计将有利于淡水蓝细菌向咸淡水的发展和扩展。由于已知淡水蓝细菌会产生毒素,因此对动物和人类健康构成了严重威胁。毒素(STX)被归类为最强大的氰毒素。因此,评估生产蓝细菌的STX面对盐度变化以及更好地了解氯化钠(NaCl)暴露的生理后果,特别是其毒性的能力变得至关重要。Dolichospermum SP )和淡水(Aphanizomenon gracileCylindrospermopsis raciborskii)确定盐度变化如何影响其生长,光合作用,色素组成,活性氧(ROS)的产生,相容性溶质的合成和STXs的细胞内配额。发现盐度耐受性是特定于物种的。Dolichospermum SP。比A. gracileC. raciborskii更能抵抗盐度变化。NaCl的变化降低了所有物种的生长。在A. gracile中,NaCl剂量依赖性地降低了类胡萝卜素的含量。相比之下,在C. raciborskii菜豆中类胡萝卜素含量的变化与NaCl浓度没有明显关系。而在Dolichospermum sp中藻蓝蛋白和藻红蛋白的第一个24小时暴露对NaCl内增大,在这两个A.竹叶C. raciborskii,这些颜料相应地降低到NaCl浓度。盐度低的变化并没有影响STXs生产A.竹叶C. raciborskii而在盐度较高的增长可以修改毒素特征曲线和内容C. raciborskii(STX内减少,而DC-GTX2增加)。在河口,A.竹叶C. raciborskii将无法在寡盐区域之外生存(即盐度> 5)。相反,部分原因是由于其具有积累相容性溶质的能力,Dolichospermum sp。有可能面临随之而来的盐度变化并在多盐地区生存的可能性(至少达到盐度= 24)。

更新日期:2021-04-08
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