Taxonomic Assessment of the Cyanobacteria from the BACA Culture Collection: Contribution to the Knowledge of Their Diversity and Monitoring in the Azores ^†

Abstract

Cyanobacteria taxonomy is changing significantly, with many new genera and species having been uncovered from a variety of cultures over the last decade. The use of cultures allowed for genetic studies using molecular markers, e.g., 16S rRNA and 16S-23S internal transcribed spacer (ITS) rRNA, complementing the morphological and ecological information traditionally used in the description of new taxa. Presently, the culture collection BACA (Azorean Bank of Algae and Cyanobacteria) comprises more than 350 strains of cyanobacteria isolated from terrestrial, aquatic, and thermal habitats in the Azores. The phylogenetic study of more than 200 strains shows new phylogenetic clades and possibly many new genera and species. Strains belonging to possible new taxa were selected for further genetic studies by 16S rRNA and 16S-23S ITS rRNA gene amplification using the 27F and 23S30R primers and sequenced. The secondary structure of the ITS gene was predicted using the mFold web server, and the D1-D1’ helix, Box-B helix and V3 helix were compared. Transmission electron microscopy was performed on simple coccoid and filamentous strains to visualize the thylakoid position in the cell. The use of a polyphasic approach enabled the identification of several new cyanobacteria taxa, supported by the phylogenetic analysis and the identification of diacritical morphological characters. The description of these new taxa contributes to the knowledge of cyanobacteria biodiversity and a better understanding of their taxonomy, which is still very confusing and problematic, allowing a better clarification of species and genera distribution.