Studies of interactive effects between iron and musty-odor producing cyanobacteria

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A recent problem for water utilities is musty-odor, which is caused by geosmin or 2-methylisoborneol produced by cyanobacteria. In order to clarify the mechanism of growth of musty-odor producing cyanobacteria, the effect of iron, an essential element, on the growth of Anabaena macrospora, Phormidium tenue, Anabaena spiroides, Oscillatoria tenuis and Oscillatoria brevis was studied.The growth was suppressed for A.macrospora, A.spiroides, P.tenue and O.tenuis in the EDTA-free CT medium. However, O.brevis grew well and produce geosmin in the EDTA-free CT medium. Thus, O.brevis showed an ability to utilize colloidal iron, iron(III) phosphate and even iron oxides for its growth. This indicates that O.brevis would be expected to produce a specific high affinity iron chelator (siderophore) in the chelator-free medium. In the presence of BPDS, a strong Fe(II) chelator, O.brevis and P.tenue were able to grow, but A.macrospora and O.tenuis were not. Furthermore, O.brevis was capable of growing in the medium containing a microbial siderophore (desferrioxamine B) or excess of strong Fe(III) chalators such as EDDHA and HBED, although the other 4 cyanobacteria were not able to grow. The growth of O.tenuis was remarkably suppressed at even high levels of iron (28 muM as Fe) when iron citrate was used as the iron source. The present studies indicate that O.brevis can utilize a wide variety of iron forms as the iron sources and more excellent ability of iron absorption compared with other 4 cyanobacteria. O.tenuis seems to have specific requirements for the iron form it can utilize for growth.