Iron-dependent expression of TonB-dependent transporters (TBDTs) of Anabaena sp. PCC 7120. (A) Anabaena sp. PCC 7120 were grown in media with (lane 1, 2, 5 and 6) and without a source of ferric ammonium citrate and copper (-Fe/-Cu, lane 3, 4, 7 and 8) as well as with (BG11, lane 1-4) and without a source of nitrogen (BG110, lane 5-8). RNA was isolated and RT-PCR was performed to visualize expression with (+) and without (-) addition of reverse transcriptase using primers listed in Table 3. The transcript of rnpB was amplified as control. (B)Anabaena sp. PCC 7120 were grown in media with (BG11, lane 1, 2) or without nitrogen source (BG110, lane 3, 4) in the absence of either copper sulfate (lane 1, 3) or ferric ammonium citrate (lane 2, 4) and RNA isolated from 50 ml cells of log phase cultures as described. RT-PCR was performed to visualize expression with and without addition of reverse transcriptase using primers listed in Table 3. (C) The results from A and B are visualized as bar code where black stands for detected expression, and white for no expression detected under conditions used. The order is given on the right (C stands for: pointing to the centre). The black outer circle marks all genes expressed in BG110, the black dashed line all genes expressed in BG11, the black dashed dotted line all genes not expressed without starvation and the dotted line the gene only weakly expressed upon copper limitation in BG11. The grey line on the outer rim indicates all genes always expressed, the grey dashed line on the outer rim all genes where expression was not detected under one condition and the grey dashed dotted line on the outer rim all genes which are expressed in BG11 and BG110, but not in all other media.