A polyphasic taxonomic approach in isolated strains of Cyanobacteria from thermal springs of Greece

[Display omitted] •Systematics of Cyanobacteria is in a state of flux.•Cyanobacteria from Greek thermal springs have been selected for cultivation and taxonomic study.•A polyphasic taxonomic approach was implemented to 17 strains of Cyanobacteria.•Among them 6 new taxa at the genus level have been proposed. Strains of Cyanobacteria isolated from mats of 9 thermal springs of Greece have been studied for their taxonomic evaluation. A polyphasic taxonomic approach was employed which included: morphological observations by light microscopy and scanning electron microscopy, maximum parsimony, maximum likelihood and Bayesian analysis of 16S rDNA sequences, secondary structural comparisons of 16S–23S rRNA Internal Transcribed Spacer sequences, and finally environmental data. The 17 cyanobacterial isolates formed a diverse group that contained filamentous, coccoid and heterocytous strains. These included representatives of the polyphyletic genera of Synechococcus and Phormidium, and the orders Oscillatoriales, Spirulinales, Chroococcales and Nostocales. After analysis, at least 6 new taxa at the genus level provide new evidence in the taxonomy of Cyanobacteria and highlight the abundant diversity of thermal spring environments with many potential endemic species or ecotypes.