Molecular phylogenetic analysis of a Gymnodinium-like species isolated from the Jiaozhou Bay of Shandong Province,China

A strain of microalgae that was isolated from the Jiaozhou Bay and primarily identified as Gymnodinium-like based on the morphological features(named as Gymnodinium sp.ZX) was further distinguished with molecular phylogenetic methods.After the processes of DNA extraction,amplification and purification,the nuclear-encoded small subunit ribosomal DNA(SSU rDNA) and internal transcribed spacer(ITS) regions were cloned and sequenced.Sequences homologous to SSU rDNA and ITS regions of Gymnodinium sp.ZX were searched with Blastn from the GenBank.The phylogenetic trees were reconstructed with the neighbor-joining(NJ) method.The results show that Gymnodinium sp.ZX has a close genetic relationship with Symbiodinium rather than Gymnodinium.Therefore,Gymnodinium sp.ZX was judged as a strain of Symbiodinium sp.Then the phylogenetic trees were reconstructed based on the SSU rDNA and ITS sequences of genus Symbiodinium respectively,the relationship among the various clades was analyzed,and Gymnodinium sp.ZX belonged to clade E.The Gymnodinium sp.ZX was isolated from the Jiaozhou Bay,and grew well in the f/2 medium,therefore,it was inferred that the free-living species of genus Symbiodinium probably existed in the Jiaozhou Bay.