Transcriptional and translational analysis of ferredoxin and flavodoxin under iron and nitrogen stress in Anabaena sp. strain PCC 7120.

In Anabaena sp. strain PCC 7120, vegetative cell ferredoxin synthesis under iron starvation was repressed 25-fold, whereas heterocyst ferredoxin synthesis decreased only 2.8-fold. Induction of flavodoxin under iron depletion was independent of the availability of combined nitrogen. Under iron stress but in the presence of combined nitrogen, fdxH and nifH genes were transcriptionally active; although excision of the 11-kb element seemed to be completed, nitrogenase activity and the fdxH gene product were not detectable.