TY - JOUR T1 - Physiological and Metabolic Responses of Freshwater and Brackish-Water Strains of Microcystis aeruginosa Acclimated to a Salinity Gradient: Insight into Salt Tolerance A1 - Georges Des Aulnois,Maxime A1 - Roux,Pauline A1 - Caruana,Amandine A1 - Réveillon,Damien A1 - Briand,Enora A1 - Hervé,Fabienne A1 - Savar,Veronique A1 - Bormans,Myriam A1 - Amzil,Zouher A1 - Atomi,Haruyuki AD - Phycotoxins Laboratory, Ifremer, Nantes, France AD - University of Rennes, CNRS, EcoBio UMR 6553, Rennes, France UR - https://doi.org/10.1128/AEM.01614-19 DO - 10.1128/AEM.01614-19 KW - acclimation KW - metabolomic KW - Microcystis KW - salinity KW - sucrose KW - trehalose KW - ecophysiology N2 - Proliferation of microcystin (MC)-producing Microcystis aeruginosa in brackish waters has been described in several locations and represents a new concern for public and environmental health. While the impact of a sudden salinity increase on M. aeruginosa physiology has been studied, less is known about the mechanisms involved in salt tolerance after acclimation. This study aims to compare the physiological responses of two strains of M. aeruginosa (PCC 7820 and PCC 7806), which were isolated from contrasted environments, to increasing salinities. After acclimation, growth and MC production rates were determined and metabolomic analyses were conducted. For both strains, salinity decreased the biovolume, growth, and MC production rates and induced the accumulation of polyunsaturated lipids identified as monogalactosyldiacylglycerol. The distinct salt tolerances (7.5 and 16.9) obtained between the freshwater (PCC 7820) and the brackish-water (PCC 7806) strains suggested different strategies to cope with the osmotic pressure, as revealed by targeted and untargeted metabolomic analyses. An accumulation of trehalose as the main compatible solute was obtained in the freshwater strain, while sucrose was mainly accumulated in the brackish one. Moreover, distinct levels of glycine betaine and proline accumulation were noted. Altogether, metabolomic analysis illustrated a strain-specific response to salt tolerance, involving compatible solute production. IMPORTANCE Blooms of Microcystis aeruginosa and the production of microcystins are major issues in eutrophic freshwater bodies. Recently, an increasing number of proliferations of M. aeruginosa in brackish water has been documented. The occurrence of both M. aeruginosa and microcystins in coastal areas represents a new threat for human and environmental health. In order to better describe the mechanisms involved in Microcystis sp. proliferation in brackish water, this study used two M. aeruginosa strains isolated from fresh and brackish waters. High salinity reduced the growth rate and microcystin production rate of M. aeruginosa. In order to cope with higher salinities, the strains accumulated different cyanobacterial compatible solutes, as well as unsaturated lipids, explaining their distinct salt tolerance. Y1 - 2019/11 PB - American Society for Microbiology JF - Applied And Environmental Microbiology SN - 0099-2240 VL - 85 IS - 21 ID - 70031 ER -