Multiple modes of iron uptake by the filamentous, siderophore-producing cyanobacterium, Anabaena sp. PCC 7120.
Iron is a member of a small group of nutrients that limits aquatic primary production. Mechanisms for utilizing iron have to be efficient and adapted according to the ecological niche. In respect to iron acquisition cyanobacteria, prokaryotic oxygen evolving photosynthetic organisms can be divided into siderophore- and non-siderophore-producing strains. The results presented in this paper suggest that the situation is far more complex. To understand the bioavailability of different iron substrates and the advantages of various uptake strategies, we examined iron uptake mechanisms in the siderophore-producing cyanobacterium Anabaena sp. PCC 7120. Comparison of the uptake of iron complexed with exogenous (desferrioxamine B, DFB) or to self-secreted (schizokinen) siderophores by Anabaena sp. revealed that uptake of the endogenous produced siderophore complexed to iron is more efficient. In addition, Anabaena sp. is able to take up dissolved, ferric iron hydroxide species (Fe') via a reductive mechanism. Thus, Anabaena sp. exhibits both, siderophore- and non-siderophore-mediated iron uptake. While assimilation of Fe' and FeDFB are not induced by iron starvation, FeSchizokinen uptake rates increase with increasing iron starvation. Consequently, we suggest that Fe' reduction and uptake is advantageous for low-density cultures, while at higher densities siderophore uptake is preferred.
Institute for Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany.
Mareike
M
Rudolf
Department of Plant and Environmental Science, The Alexander Silberman Institute of Life Sciences, The Hebrew University in Jerusalem, Jerusalem, Israel.
Chana
C
Kranzler
Department of Plant and Environmental Science, The Alexander Silberman Institute of Life Sciences, The Hebrew University in Jerusalem, Jerusalem, Israel.
Hagar
H
Lis
Department of Plant and Environmental Science, The Alexander Silberman Institute of Life Sciences, The Hebrew University in Jerusalem, Jerusalem, Israel.
Ketty
K
Margulis
Institute for Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany.
Mara
M
Stevanovic
Department of Plant and Environmental Science, The Alexander Silberman Institute of Life Sciences, The Hebrew University in Jerusalem, Jerusalem, Israel.
Nir
N
Keren
Institute for Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany.|Cluster of Excellence Macromolecular Complexes, Goethe University Frankfurt, Frankfurt, Germany.|Buchman Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany.
Enrico
E
Schleiff
D017033:Anabaena / Q000378:metabolism*; D001692:Biological Transport; D007501:Iron / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D017262:Siderophores / Q000378:metabolism*
D017262:Siderophores; D007501:Iron