Studies on Cyanobacterial Cyderophores

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Cyanobacteria are the prokaryotic phytoplankton and the representative primary producer in aquatic environment. They perform oxygenic photosynthesis using various iron-containing catalysis, and many species of them can also fix nitrogen by the iron-rich enzyme, nitrogenase. However little is known about the molecular mechanism to acquire the iron of cyanobacteria. In this report, I reported the first genuine Cyanobacterial siderophores from the freshwater cyanobacteria with nitrogen fixation ability.1. Screening for siderophore productive activity of various freshwater Cyanobacterial speciesFor large-scale screening, 41 axenic strains of freshwater cyanobacteria were selected and obtained from four culture collections, NIES, PCC, UTEX and IAM. In this screening, all strains of Microcystis aeruginosa did not show siderophore productive activity. The other noticeable result in this screening was that most of heterocystous diazotrophic species produced siderophores. This result gave me a … More hypothesis that heterocystous species had the faculty of producing siderophores to maintain their nitrogenase, an iron-rich protein, for nitrogen fixation.2. Anachelins, novel siderophores produced by Anabaena cylindrica NIES-19Novel Cyanobacterial siderophores, Anachelin-2 and Anachelin were isolated from Anabaena cylindrica NIES-19. The molecular formula of these compounds were determined to be C35H49013N6 from HRFAB-MS analysis. These structures were decided 2D NMR analyses including COSY, HMQC, 1H-13C HMBC, and 1H-15N HMBC experiments.3. Schizokinen, a siderophore produced by two strains of Anabaena variabilis M-204 and NIES-23Isolated siderophores from A. variabilis(M-204, NIES-23) were also positive in the Csaky test, indicating that this compound was a hydroxamate-type siderophore, schizokinen. The structure of schizokinen was confirmed by NMR analysis.4. Oscillabactin, a novel siderophore produced by Oscillatoria tenuis UTEX1566We isolated a novel Cyanobacterial siderophore, oscillabactin from Oscillatoria tenuis UTEX 1566. Oscillabactin is the first siderophore containing the hydroxypyridinone structure as the iron-binding group. Less