IFREMER-Phycotoxins Laboratory, IFREMER, F-44311 Nantes, France.
Department of Microbiology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany.
Toxins (Basel). 2020 Mar 18;12(3):192. doi: 10.3390/toxins12030192.
The transfer of from freshwater to estuaries has been described worldwide and salinity is reported as the main factor controlling the expansion of to coastal environments. Analyzing the expression levels of targeted genes and employing both targeted and non-targeted metabolomic approaches, this study investigated the effect of a sudden salt increase on the physiological and metabolic responses of two toxic strains separately isolated from fresh and brackish waters, respectively, PCC 7820 and 7806. Supported by differences in gene expressions and metabolic profiles, salt tolerance was found to be strain specific. An increase in salinity decreased the growth of with a lesser impact on the brackish strain. The production of intracellular microcystin variants in response to salt stress correlated well to the growth rate for both strains. Furthermore, the release of microcystins into the surrounding medium only occurred at the highest salinity treatment when cell lysis occurred. This study suggests that the physiological responses of involve the accumulation of common metabolites but that the intraspecific salt tolerance is based on the accumulation of specific metabolites. While one of these was determined to be sucrose, many others remain to be identified. Taken together, these results provide evidence that is relatively salt tolerant in the mesohaline zone and microcystin (MC) release only occurs when the capacity of the cells to deal with salt increase is exceeded.
从淡水到河口的转移已在全球范围内得到描述，盐度被报道为控制扩展到沿海环境的主要因素。本研究通过分析靶基因的表达水平，并采用靶向和非靶向代谢组学方法，研究了突然增加盐度对分别从淡水和微咸水分离的两种有毒 PCC 7820 和 7806 菌株的生理和代谢反应的影响。受基因表达和代谢谱差异的支持，盐耐受性被发现是菌株特异性的。盐度增加会降低藻类的生长，对微咸水菌株的影响较小。微囊藻毒素变体的产生对两种菌株的生长速率与盐胁迫的反应都很好。此外，只有在细胞裂解发生时，才会在最高盐度处理时将微囊藻毒素释放到周围介质中。本研究表明，藻类的生理反应涉及常见代谢物的积累，但种内盐耐受性是基于特定代谢物的积累。虽然其中一种被确定为蔗糖，但仍有许多有待鉴定。总之，这些结果表明，在中盐区藻类相对耐盐，并且只有当细胞应对盐度增加的能力超过时才会发生微囊藻毒素（MC）释放。
