Iron mediated regulation of growth and siderophore production in a diazotrophic cyanobacterium Anabaena cylindrica.

Iron mediated regulation of growth and siderophore production has been studied in a diazotrophic cyanobacterium Anabaena cylindrica. Iron-starved cells of A. cylindrica exhibited reduced growth (30%) when the cells were growing under N2-fixing conditions. In contrast, N03-, NO2-, NH4' and urea grown cells exhibited almost 50% reduction in their growth in the absence of iron as compared to their respective counterparts cultured in the presence of iron. However, at 60 microM of iron, A. cylindrica cells exhibited almost equal growth regardless of the nitrogen source available. Siderophore production in A. cylindrica was started after day 2nd of the cell growth and attained its optimal level on day 5th when the cells were at their mid-log phase. No siderophore production was, however, recorded on day 2nd at all the concentrations of iron tested. The production of siderophore in A. cylindrica further increased with increase in iron concentration and attained its optimum level on day 5th at 60 microM iron. A. cylindrica cells took at least 3 days for initiation of siderophore production and produced about 60% siderophore on day 5th even under iron-starved condition. A. cylindrica produced dihydroxamate type of siderophore.

Iron induced metabolic changes in the diazotrophic cyanobacterium Anabaena PCC 7120.

Iron induced changes in growth, N2-fixation, CO2 fixation and photosynthetic activity were studied in a diazotrophic cyanobacterium Anabaena PCC 7120. Iron at 50 microM concentration supported the maximum growth, heterocyst frequency, CO2 fixation, photosystem I (PS I), photosystem II (PS II) and nitrogenase activities in the organism. Higher concentration of iron inhibited these processes. Chl a and PS II activities were more sensitive to iron than the protein and PS I activity.