IRON FORMS THAT INFLUENCE THE GROWTH AND MUSTY ODOR PRODUCTION OF SELECTED CYANOBACTERIA

In order to clarify the mechanism of growth of musty-odor producing cyanobacteria, the effects of iron forms on growth and musty-odor production in four species of cyanobacteria, Oscillatoria brevis, Anabaena macrospora, Phormidium tenue and Oscillatoria tenuis were studied using laboratory batch cultures. The former two cyanobacteria produce geosmin and the latter two produce 2-methylisoborneol (MIB). The growth of A. macrospora, P. tenue and 0. tenuis was suppressed in the EDTA (chelating agent) - free CT medium. However, 0. brevis grew well and produced geosmin in this medium as well as in the presence of EDTA. Thus, 0. brevis showed an ability to utilize colloidal iron and even iron oxides for its growth. This suggests that 0. brevis would be expected to produce a specific high affinity iron chelator (siderophore) in the chelator-free medium. In the presence of bathophenanthroline disulfonate (BPDS), a strong Fe(II) chelating agent, 0. brevis and P. tenue were able to grow, but A. macrospora and 0. tenuis did not. Furthermore, 0. brevis was capable of growing in the medium containing a microbial siderophore, desferrioxamine B(DESF), instead of EDTA, but the other three cyanobacteria did not grow. These results show that 0. brevis has an excellent ability to utilize a variety of iron forms including Fe(III) - EDTA, Fe(II) - BPDS, Fe(III) - DESF chelates, colloidal ferric hydroxide and more thermodynamically stable crystalline iron oxides (Fe203 and Fe304) in comparison with the other three musty-odor producing cyanobacteria isolated from Lake Biwa.