16S rRNA-based phylogenetic tree summarizing the presence or absence of Yfr1 in all major cyanobacterial lineages. Cyanobacteria for which genome sequences are currently available from public databases are in boldface letters. Those strains, for which a Yfr1 ncRNA was computationally predicted are labeled Yfr1+. Those, for which we provide experimental evidence for the presence of Yfr1 are labeled Yfr1*. We have shown the presence of Yfr1 in the Prochlorococcus strains MED4 and MIT9313 and in Synechococcus WH 8102 before . The tree is based on a multiple sequence alignment of 16S rRNA sequences analyzed in MEGA3.1 . Statistic support values were generated by bootstrapping and are only shown if > 70. The 16S rRNA of Chlorobium tepidum TLS served as an outgroup. The sections I-V of cyanobacterial taxonomy  are indicated.