Coincidences of structural and molecular characters in evolutionary lines of cyanobacteria

The traditional system of cyanobacteria based on morphological characters is in agreement with the molecular phylogenetic tree derived from 16S rRNA sequencing only in complicated, morphologically clearly diversified groups (heterocytous orders). The molecular evaluations of simple cyanobacteria yield a mixture of coccoid and filamentous (oscillatorialean) strains indicating the more complicated relations and heterogeneity of these groups. The evaluation of phenotype and molecular markers resulted in several conclusions: (i) The basic fine structures (thylakoidal patterns) are more or less in agreement with clusters derived from molecular sequencing; (ii) the coccoid types are particularly heterogeneous, and different groups of unicellular and colonial strains are more related to different consequent clusters of filamentous cyanobacteria than mutually one to another; (iii) it means, that several phylogenetically separated lines exist in cyanobacteria with more or less congruent type of cell structure; and (iv) each of these lines contains both special coccoid and simple trichal types. The taxonomic classification should be re-evaluated according to mentioned criteria.