Salt acclimation of Nodularia spumigena CCY9414—a cyanobacterium adapted to brackish water

Abstract

The toxic cyanobacterium Nodularia spumigena regularly forms large surface blooms in the central Baltic Sea. The Baltic Sea is characterized by a salinity gradient. We analyzed the salt acclimation of the strain N. spumigena CCY9414, the only Nodularia strain with a known genome sequence. N. spumigena CCY9414 showed a rather low salt tolerance range, displaying a growth optimum at 12.5 g NaCl l −1. Sucrose was identified as the major compatible solute. The expression of the sucrose-phosphate synthase gene was salt-stimulated, which indicates that the salt-induced sucrose accumulation could be regulated at the transcriptional level. Potassium ions and glutamate were also accumulated in Nodularia cells, especially at high salinities when sucrose levels were rather low. Our results indicate that N. spumigena CCY9414 represents a truly brackish-water-adapted cyanobacterial strain. KEY WORDS: Compatible solute · Glutamate · Potassium · SucroseResale or republication not permitted without written consent of the publisher Aquat Microb Ecol 70: 207-214, 2013 west connection to the North Sea and almost freshwater conditions in the Northern and Eastern edges (Samuelsson 1996). The distribution of Nodularia spumigena could depend on the external salinity because blooms occur mostly in the central Baltic Sea characterized by brackish waters around 8 practical salinity units (PSU) (Feistel et al. 2010). To adjust the internal osmotic potential to changing salinities, cyanobacteria are known to accumulate specific classes of compatible solutes (Hagemann 2011). Members of the group Nostocales, such as the model strain Anabaena sp. PCC 7119, usually show optimal growth under fresh water conditions and can acclimate to brackish water salinities by the accumulation of sucrose, which is catalyzed by sucrose-phosphate synthase (SPS) (Porchia & Salerno 1996).Compared to freshwater Anabaena strains, Nodularia spumigena seems to prefer brackish water conditions. To get deeper insight into the basic saltacclimation strategy of this ecologically important cyanobacterial genus, we aimed to investigate the salt response of N. spumigena under defined laboratory conditions. For this purpose, we used the Baltic Sea isolate N. spumigena CCY9414 (hereafter Nodularia CCY9414), taking advantage of its known genome sequence (GenBank accession no. AAVW 00000000; Voß et al. 2013). Genome searches revealed that Nodularia CCY9414 is potentially able to synthesize sucrose as well as trehalose as compatible solutes. Our results suggest that Nodularia CCY9414 is a brackish-water-adapted cyanobacterium because it grew optimally at salinities around 10 g NaCl l −1 and accumulated sucrose as the main compatible solute under these conditions. MATERIALS AND METHODS Strain and cultivationNodularia spumigena CCY9414 was obtained from the Culture Collection Yerseke (CCY) at the Netherlands Institute of Sea Research (NIOZ). This Baltic Sea strain was isolated from surface waters of ~9 PSU east of the island of Bornholm. It was taken into the strain ...

Toxin Analysis of Freshwater Cyanobacterial and Marine Harmful Algal Blooms on the West Coast of Florida and Implications for Estuarine Environments

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Comparative Genomics of the Baltic Sea Toxic Cyanobacteria Nodularia spumigena UHCC 0039 and Its Response to Varying Salinity

“…Nodularia dominates in more saline parts (Halinen et al, 2007 ; Sivonen et al, 2007 ). The optimal salt concentration for Baltic Sea Nodularia spumigena CCY9414 growth was previously found to be 12.5 g L −1 NaCl, which is the salinity prevailing in the southern regions of the Baltic Sea (Möke et al, 2013 ).…”

“…These results also matched the observations by Voß et al ( 2013 ) on the expression of these genes in Nodularia CCY9414. In addition, accumulation of compatible solutes was measured in Nodularia CCY9414, and sucrose appeared to be the major compatible solute (Möke et al, 2013 ). The possible role of trehalose as a compatible solute in brackish water ecosystems is thus questionable and needs more investigations.…”

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