Phylogenetic maximum likelihood (ML) tree based on the concatenated 23S-16S rDNA sequences of diverse cyanobacterial lineages. The sequences were taken from public databases. Strain identifiers, and the methods used for the phylogenetic analysis, are described in the Methods section. The scale bar represents the average number of nucleotide substitutions per site. Genome sizes in megabases (Mb) are mentioned in parentheses. Trees were constructed using three methods (ML, Neighbor Joining and Maximum Parsimony). ML bootstrap values are indicated only if the bootstrap values obtained with the three methods are > 500 (1000 resamplings).