THE ROLE OF IRON IN THE GROWTH OF MUSTY-ODOR PRODUCING CYANOBACTERIA IN THE LAKE ECOSYSTEM

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In order to clarify the role of iron in the growth of musty-odor producing cyanobacteria, the effcts of iron on the growth of Oscillatoria tenuis, Anabaena macrospora, Anabaena spiroides, Phormidium tenue and Oscillatoria brevis were studied. A.macrospora, A.spiroides and O.brevis produce geosmin and O.tenuis and P.tenue produce 2-methylisoborneol (MIB). The growth of A.macrospora, A.spiroides and O.tenuis was suppressed at low levels of colloidal iron in the EDTA (chelating agent) -free medium. O.tenuis was found to require chelated and photoreducible iron for its growth. The effects of seven chelating agents on the growth of above musty-odor producing cyanobacteria were studied using laboratory cultures. O.tenuis, A.macrospora, A.spiroides, P.tenue and O.brevis grew well in the presence of EDTA,CyDTA,DTPA,EDDHA,HBED in the presence of 1 : 1 ratio of chelating agent to iron. However, the growth of O.tenuis, A.macrospora and A.spiroides was suppressed in the presence of large amounts of DTPA,EDDHA and HBED.O.brevis was found to have the ability to utilize a wide variety of iron forms such as Fe-EDTA,Fe^<II> (BPDS) _3, spongy iron, powdery iron, Fe (III) -Desferrioxamine B (microbial siderophore) chelates, colloidal ferric hydroxides and more thermodynamically stable crystalline iron oxides. O.brevis was found to have stronger abilities for the chelation of Fe (III) and absorption of iron compared with O.tenuis, A.macrospora, A.spiroides and P.tenue. O.tenuis seems to have very specific requirements for the form of iron it can utilize for growth.