Spearman’s rank correlation coefficient (ρ) and Pearson’s correlation coefficient (R) are displayed above the corresponding graph. Positive correlation coefficients of rRNA gene copies to terminally differentiated cyanobacteria are supported. Using Spearman’s rank correlation coefficient (ρ) and

Pearson’s correlation coefficient (R), GDC-0449 concentration we estimated a potential correlation of copy numbers to the defined morphological groups. Both tests indicated significant correlations to morphological groups for all ribosomal genes and two transposase coding genes. Furthermore, Spearman’s ρattested a significant correlation to morphology for photosystem II reaction center D2 protein (ρ=0.62), and a weaker correlation to Gas vesicle protein GVPa (ρ=0.58) coding genes. A significant Pearson’s correlation was found for a gene coding for a hypothetical protein (R=0.58). In Figure 3 distributions of ribosomal RNA gene copy numbers across morphological groups are presented as boxplot graphics with correlation coefficients, and p-values shown. All taxa capable of terminal differentiation

exhibited four copies of ribosomal RNA genes. Correlation coefficients for 16S and 23S rRNA genes were ρ=0.74/R=0.86, in both cases, and ρ=0.63/R=0.8 for the 5S rRNA genes. Including AZD2014 nmr additional data from the rrn-database [45] (Additional file 2), resulted in an even stronger correlation of 16S rRNA gene copy numbers to cyanobacterial species capable of terminal differentiation (ρ=0.87/R=0.9; Additional file 3). Cyanobacteria belonging to section IV and V form terminally differentiated cells (called heterocysts) in the absence of fixed nitrogen. In these cells oxygen sensitive nitrogen fixation can take place while neighbouring cells conduct oxygenic photosynthesis. These heterocystous cells

undergo various structural and physiological alterations to protect nitrogenase from oxygen in a ‘microanaerobic’ environment. As a result they lose their ability to conduct photosynthesis and to divide. Multiple rRNA gene copies could have positive effects during heterocyst formation, the same way as they help E.coli to achieve maximum growth [12], and increases responses to changing environmental conditions [11]. An increased amount of functional ribosomal operons likely depicts an advantage in the process of cell differentiation, during which expression of various genes is upregulated [46]. Strong conservation of 16S rRNA copies Sclareol Previous studies have sometimes questioned the potential of 16S rRNA gene sequences as a taxonomic marker due to variation that has been observed between gene paralogs in some non-cyanobacterial organism [10, 34]. We explored sequence variation of 16S rRNA genes in cyanobacteria by reconstructing phylogenetic trees with Bayesian inference. We evaluated the divergence of 16S rRNA gene copies within and between cyanobacterial taxa. The inferred Bayesian consensus tree is displayed in Figure 2. Investigated cyanobacteria, exhibit one to four 16S rRNA copies per genome.