Effect of iron deficiency on ferredoxin levels in Anabaena variabilis PCC 6309

Cultures of the nitrogen-fixing cyanobacterium Anabaena variabilis PCC 6309 were grown under several iron concentrations, and changes in growth rates and chlorophyll and phycocyanin concentrations were determined. The total amount of ferredoxin present in the cells was found to be dependent on the concentration of iron in the media, as was the pattern distribution of the two different forms of the iron-sulfur protein described in this organism. Flavodoxin was not found to be present in these cells even when they were grown in the absence of added iron, indicating that this flavoprotein does not replace ferredoxin in this particular strain.