Isolation and Characterization of Dunaliella Species from Sambhar Lake (India) and its Phylogenetic Position in the Genus Dunaliella Using 18S rDNA

High beta-carotene producing microalga Dunaliella, isolated from Sambhar Lake, India, was identified, characterized and analyzed for its phylogenetic position in the genus Dunaliella. It was characterized on the basis of morphology and 1.7 Kb PCR product produced using the primers MA1 and MA2 which is specific to Dunaliella. Four stress parameters were used for characterization i.e. NaCl concentration, temperature, light and nitrogen concentration. On these parameters total cell number, specific growth rate and total carotenoids/chlorophyll a ratio was analyzed. 1.7 M NaCl, 26 A degrees C temperature, diurnal light and 4.9 mM N-concentration were identified as optimum conditions for growth whereas 3.5 M NaCl, 37 A degrees C temperature, continuous light and without nitrogen source were identified as optimum conditions for carotenoid production. Highest cell number (19.6 x 10(5) cells/ml) and specific growth rate (0.505 division per day) were observed at 1.7 M salinity whereas highest total carotenoids/chlorophyll a ratio (1.57) was observed at 3.5 M salinity. 17 sequences of 18S rDNA of Dunaliella, taken from NCBI nucleotide database, were used for phylogenetic analysis. A bootstrap consensus tree was constructed using neighbour-joining method.