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A halotolerant cyanobacterium Aphanothece halophytica thrives in extreme salinity with accumulation of a potent osmoprotectant glycine betaine. Recently, this cyanobacterium was shown to accumulate sunscreen molecule mycosporine-2-glycine significantly at high salinity. In this study, we investigated effects of nitrate and amino acid provision on the accumulation of glycine betaine and mycosporine-2-glycine. With elevated nitrate concentrations at high salinity, intracellular levels of both metabolites were enhanced. Six-fold high nitrate concentration increased the relative amounts of glycine betaine and mycosporine-2-glycine to be 1.5 and 2.0 folds compared with control condition. Increased levels were time- and dose-dependent manner. Exogenous supply of glycine/serine at high salinity resulted in the similar trends as observed in excess nitrate experiment. Intracellular level of glycine betaine increased -1.6 folds with glycine/serine supplementation. These supplementations also caused the increased level of mycosporine-2-glycine, namely 1.4 and 2 folds by glycine and serine, respectively. The transcription of glycine betaine and mycosporine-2-glycine biosynthetic genes was strongly induced under high-nitrate-salt condition. These results suggest the dependence of glycine betaine and mycosporine-2-glycine productions on substrate availability, and the effect of nitrate was possibly associated with stimulation of osmoprotectant increment in this extremophile. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study revealing that a fresh water Chlorella vulgaris TISTR 8580 contains a salt-induced heme-protein caleosin. Topics mentioned include the accumulation of triacylglycerol being induced under salt-stressed condition, cloning of putative caleosin gene from C. vulgaris TISTR 8580, and expression of caleosin gene in Escherichia coli.

The article focuses on a research on cation symporters in cyanobacterium Aphanothece halophytica. Topics discussed include role of amino acid-polyamine-organocation (APC) as active amino acid transporters, uptake of inorganic nitrogens like ammonium and nitrate for nitrogen assimilation and, role of glutamine as nitrogen source for cyanobacteria.