Iron mediated regulation of growth and siderophore production in a diazotrophic cyanobacterium <i style="">Anabaena cylindrica</i>

Abstract

Iron mediated regulation of growth and siderophore production has been studied in a diazotrophic cyanobacterium <i style="">Anabaena cylindrica</i>. Iron-starved cells of <i style="">A. cylindrica</i> exhibited reduced growth (30%) when the cells were growing under N₂-fixing conditions. In contrast, NO₃^-, 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 μ<i style="">M</i> of iron, <i style="">A. cylindrica </i>cells exhibited almost equal growth regardless of the nitrogen source available. Siderophore production in <i style="">A. cylindrica</i> was started after day 2^nd of the cell growth and attained its optimal level on day 5^th when the cells were at their mid-log phase. No siderophore<i style=""> </i>production was, however, recorded on day 2^nd at all the concentrations of iron tested. The production of siderophore in <i style="">A. cylindrica</i> further increased with increase in iron concentration and attained its optimum level on day 5^th at 60 μ<i style="">M</i> iron. <i style="">A. cylindrica</i> cells took at least 3 days for initiation of siderophore production and produced about 60% siderophore on day 5^th even under iron-starved condition. <i style="">A. cylindrica</i> produced dihydroxamate type of siderophore.