Planktic cyanobacteria from freshwater localities in Thuathien-Hue province, Vietnam. III. Phylogenetic inference based on partial phycocyanin sequences, morphological and toxicological characters

The morphology, toxicity and partial sequences of beta and alpha subunits including the intergenic spacer (cpcBA-IGS) of the phycocyanin operon were studied in 21 strains of nonaxenic cyanobacterial cultures. The cultures were established from water samples collected in the Thuathien Hue province in Vietnam, 2004. Based on testing for the presence of the mcyA gene, microcystin-production of Microcystis aeruginosa, M. botrys and M. panniformis was confirmed. The presence of the mcyA gene in a strain of Microcystis flos-aquae and a strain of Planktothrix spiroides (HA308) revealed their toxic potential. The phylogeny of the Vietnamese cyanobacteria was inferred using sequences encoding the cpcBA genes. There was no correlation between toxic characters based on ELISA, HPLC and mcyA gene and the phylogeny based on partial cpcBA sequences. Although the resulting tree topology assisted in resolving the phylogeny of some strains of Anabaena, Dolichospermum and Planktothrix, taxonomical problems still exist at the species level for Lyngbya and Microcystis. Future morphological and molecular studies will have to solve these issues.