Detection of Yfr1 RNA in seven different freshwater cyanobacteria. A. About 10 μg of total RNA from Synechococcus sp. PCC 7942 (Syn 7942), Thermosynechococcus elongatus BP1 (Tsyn. elong.), Synechocystis PCC 6803 (Sync. 6803), Microcystis aeruginosa PCC 7806 (Mic. 7806), Nostoc sp. PCC 7120 (Nos. 7120), Nostoc punctiforme (Nos. punct.) and Gloeobacter violaceus PCC 7421 (Gloe. 7421) was analyzed by staining a 10% polyacrylamide gel with ethidium bromide.B. Northern blot hybridization with DNA oligonucleotides for the presence of Yfr1 (lower part) and, as a control, the 6S RNA (upper part).