Interaction of microalgae and bacteria is often obligatory for microalgae proliferation. Here, we investigated the specific bacterial communities associated with Alexandrium tamarense and Cochlodinium polykrikoides, both of which cause ecological and economical damage during blooms. Method for selective isolation of the bacterial metagenome from the DNA rich dinoflagellate were developed and subsequently used for 16s-rRNA metagenome analysis. In addition to the conventional method of sequencing the V3-V4 hypervariable regions with Illumina platform, the full length 16s rRNA gene were sequenced by MinION Nanopore sequencer.