Taxonomic re-evaluation of Aphanizomenon flos-aquae NH-5 based on morphology and 16S rRNA gene sequences

The taxonomy of Aphanizomenon flos-aquae strain NH-5, a producer of cyanoto xins, was re-evaluated by comparison with six other Aphanizomenon strains u sing morphological characteristics and 16S rRNA gene sequences. Strain NH-5 was concluded to be improperly identified as Aph. flos-aquae based upon (1 ) lack of bundle formation in the trichomes, (2) location of akinetes next to heterocytes, (3) lower similarities (less than 97.5%) in the 16S rRNA ge ne sequences relative to Aph. flos-aquae strains, and (4) comparison within a phylogenetic tree constructed from 16S rRNA gene sequences. The Aphanizo menon strains investigated in this study are classified to four morphologic al groups as described by the classical taxonomy of Komarek & Kovacik (1989 ). This classification was supported from the phylogenetic results of 16S r RNA gene sequences. This study also discusses the generic boundaries betwee n Aphanizomenon and Anabaena.