Culture-dependent and -independent Analyses of Bacterial Assemblages within Microalgae Cultures

초록

Microalgae are important primary producers in aquatic ecosystems and are also biological resources with many industrial uses. Growth of many microalgae are known to be dependent on co-occurring bacteria, suggesting the importance of interaction between microalgae and heterotrophic bacteria. Here, we analyzed bacterial assemblages within cultures of four microalgae (Tetraselmis sp. KCTC 12236BP and KCTC 12432BP, Dunaliella tertiolecta LB999, and Synechocystis sp. PCC6803), using culture-dependent and -independent methods. Amplicon sequencing showed that bacterial communities of the microalgal cultures were dominated by several genera, such as Oricola (19% of amplicon sequences; Tetraselmis sp. KCTC 12236), Algoriphagus (56%; Tetraselmis sp. KCTC12432), Winogradskyella (55%; Dunaliella), and Mesorhizobium (64%; Synechocystis). Several bacterial strains isolated by dilution-to-extinction culturing and dilution plating were found to represent bacterial assemblages of the microalgal cultures. For example, 16S rRNA gene sequence of a Winogradskyella strain isolated from Dunaliella culture showed >99.5% identity with 46% of the amplicon sequences from the same culture. A Mesorhizobium strain from Synechocystis culture also had 16S rRNA gene sequence nearly identical to 56% of amplicons. Further studies on these microalgae and bacterial isolates would contribute to our understanding on microalgae-bacteria interaction. [Supported by the Collaborative Genome Program of KIMST funded by the MOF, Korea]