Isolation and Characterization of Bacteria Associated with a Marine Dinoflagellate and Studies on the Interaction with Microalgae

Abstract

Microalgae were investigated for their growth interaction with bacteria isolated from dinoflagellate, Prorocentrum minimum. An axenic culture of microalga were obtained by repeated treatment of the antibiotic cocktail at different concentrations. The axenic microalga were then co-inoculated with three bacteria, arbitrarily designated as white, yellow and pink to test the growth promotion of the each algae. A sequence analysis of the 16S rRNA gene of bacterial strains it’s showed 99%, 98% and 99% nucleotide sequence similarity to that of Marinobacter sp., Muricauda aquimarina and Cyclobacterium amurskyense respectively. Based on the result of the study, the optimum growth for these 3 strains of bacteria was observed at pH 8, 2% NaCl concentrations and 37℃ temperature. In the co-culture of C. vulgaris and bacteria, it was observed that there were no significant difference in their growth after six days of inoculation even with or without the bacterial presence the microalgae can still grow. In the co-culture of N. oceanica and bacteria the most effective among the three was Marinobacter sp. which increased the growth of microalgae after six days of culture. In the co-culture of Nannochloropsis sp. with the three bacterial strains, the result showed that all of the bacteria enhanced for the growth of microalgae. All bacterial strains have different stimulatory effect on the growth of microlaga. The results of this studies implied that the growth interactions between bacteria and microalgae are species-specific.