The effect of suboptimal growth temperature on d-carotene and fatty acid biosynthesis, and on the... more The effect of suboptimal growth temperature on d-carotene and fatty acid biosynthesis, and on the ultrastructural reorganization of the chloroplast, in the green unicellular alga Dunaliella salina has been studied. A decrease from the optimal temperature for growth (30°C) to suboptimal (I8°C) temperatures induced d-carotene synthesis and increased lipid content in D. salina cells, thereby promoting the formation of lipid-carotene globules in the chloroplast periphery. The content of polyunsaturated fatty acids was higher in cells cultured at low temperature. Results suggest that the induction of carotenogenesis and accumulation of polyunsaturated fatty acids are mechanisms of acclimation to unfavourable environmental conditions for growth.
Dunaliella acidophila is one of the most extreme acidophiles on earth and is able to survive in h... more Dunaliella acidophila is one of the most extreme acidophiles on earth and is able to survive in highly acidic habitats. This characteristic has made this organism the universal model for the study of abiotic stress. Although D. acidophila is currently circumscribed to the subgenus Pascheria within Dunaliella Teodoresco (Chlorophyceae), its taxonomic position has stirred controversy. The comparison of D. acidophila CCAP19/35 internal transcribed spacers (including ITS2 secondary structure analysis) and RuBisCo large subunit (rbcL) sequences with other Dunaliella species confirms that D. acidophila should maintain its phylogenetic position within the genus Dunaliella, suggesting its inclusion within the subgenus Dunaliella. Furthermore, the ITS1 and ITS2 data revealed that D. acidophila was highly divergent from the other freshwater species assessed, D. lateralis, with which it barely shares a 56.8% similarity.
The variation of the fatty acid profile and the carotene content of Dunaliella salina in response... more The variation of the fatty acid profile and the carotene content of Dunaliella salina in response to irradiance (80, 128, 640, 1000, 1500 μmol photon m−2 s−1) and nitrogen starvation were analysed. The highest fatty acid content per cell and the least polyunsaturated fatty acid percentage were exhibited under 1500 μmol photon m−2 s−1. Furthermore, the oleic acid (18:1) content maintained a positive and significant correlation with the carotene content per cell and with the irradiance. The composition of the carotene globules in Dunaliella salina may be the main determinant of this correlation.
Financial support: This research was partially supported by Interreg IIIB European programme, Pro... more Financial support: This research was partially supported by Interreg IIIB European programme, Project 159-SAL, the FCT research project OVERCAROTEN POCTI/MAR/15237/99 and the Portuguese national budget.
Since flow cytometry allows rapid,simultaneous and quantitative measurementsrelated to cell morph... more Since flow cytometry allows rapid,simultaneous and quantitative measurementsrelated to cell morphology andphysiologicy, the lipid-specificfluorescent dye, Nile Red, was employed forthe in vivo lipid quantification of Crypthecodinium cohnii, a heterotrophicmarine dinoflagellate rich inpolyunsaturated long chain fatty acids. Thefluorescence signal was linearly correlatedwith the neutral and polar lipid content asdetermined by gravimetric techniques. Asignificant correlation of NR signal wasalso observed between the polar to neutrallipid ratio and docohexaenoic acid percell. The results demonstrate a method forrapid lipid quantification that can be usedin the selection, isolation and culturecontrol of C. cohnii clones with highlipid and DHA content.
The effect of suboptimal growth temperature on d-carotene and fatty acid biosynthesis, and on the... more The effect of suboptimal growth temperature on d-carotene and fatty acid biosynthesis, and on the ultrastructural reorganization of the chloroplast, in the green unicellular alga Dunaliella salina has been studied. A decrease from the optimal temperature for growth (30°C) to suboptimal (I8°C) temperatures induced d-carotene synthesis and increased lipid content in D. salina cells, thereby promoting the formation of lipid-carotene globules in the chloroplast periphery. The content of polyunsaturated fatty acids was higher in cells cultured at low temperature. Results suggest that the induction of carotenogenesis and accumulation of polyunsaturated fatty acids are mechanisms of acclimation to unfavourable environmental conditions for growth.
Dunaliella acidophila is one of the most extreme acidophiles on earth and is able to survive in h... more Dunaliella acidophila is one of the most extreme acidophiles on earth and is able to survive in highly acidic habitats. This characteristic has made this organism the universal model for the study of abiotic stress. Although D. acidophila is currently circumscribed to the subgenus Pascheria within Dunaliella Teodoresco (Chlorophyceae), its taxonomic position has stirred controversy. The comparison of D. acidophila CCAP19/35 internal transcribed spacers (including ITS2 secondary structure analysis) and RuBisCo large subunit (rbcL) sequences with other Dunaliella species confirms that D. acidophila should maintain its phylogenetic position within the genus Dunaliella, suggesting its inclusion within the subgenus Dunaliella. Furthermore, the ITS1 and ITS2 data revealed that D. acidophila was highly divergent from the other freshwater species assessed, D. lateralis, with which it barely shares a 56.8% similarity.
The variation of the fatty acid profile and the carotene content of Dunaliella salina in response... more The variation of the fatty acid profile and the carotene content of Dunaliella salina in response to irradiance (80, 128, 640, 1000, 1500 μmol photon m−2 s−1) and nitrogen starvation were analysed. The highest fatty acid content per cell and the least polyunsaturated fatty acid percentage were exhibited under 1500 μmol photon m−2 s−1. Furthermore, the oleic acid (18:1) content maintained a positive and significant correlation with the carotene content per cell and with the irradiance. The composition of the carotene globules in Dunaliella salina may be the main determinant of this correlation.
Financial support: This research was partially supported by Interreg IIIB European programme, Pro... more Financial support: This research was partially supported by Interreg IIIB European programme, Project 159-SAL, the FCT research project OVERCAROTEN POCTI/MAR/15237/99 and the Portuguese national budget.
Since flow cytometry allows rapid,simultaneous and quantitative measurementsrelated to cell morph... more Since flow cytometry allows rapid,simultaneous and quantitative measurementsrelated to cell morphology andphysiologicy, the lipid-specificfluorescent dye, Nile Red, was employed forthe in vivo lipid quantification of Crypthecodinium cohnii, a heterotrophicmarine dinoflagellate rich inpolyunsaturated long chain fatty acids. Thefluorescence signal was linearly correlatedwith the neutral and polar lipid content asdetermined by gravimetric techniques. Asignificant correlation of NR signal wasalso observed between the polar to neutrallipid ratio and docohexaenoic acid percell. The results demonstrate a method forrapid lipid quantification that can be usedin the selection, isolation and culturecontrol of C. cohnii clones with highlipid and DHA content.
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