Effect of Chelating Agents on the Absorption of Iron by Phormidium tenue

Abstract

In order to clarify the mechanism of growth of musty-odor producing cyanobacteria, the effect of seven chelating agentssuch as EDTA (Ethylenediaminetetraacetic acid), CyDTA (Trans-1, 2-cyclohexanediamine-N, N, N′, N′-tetraacetic acid), DTPA (Diethylenetriamine-N, N, N′, N″, N″-pentaacetic acid), EDDHA {Ethylenediaminedi (o-hydroxyphenylacetic acid) }, HBED {N, N′-di (2-hydroxylbenzyl) -ethylenediamine-N, N′-diacetic acid}, DESF (Desferrioxamine B), BPDS (Bathophenanthroline disulfonate) on the growth ofPhormidium tenuewere studied using laboratory cultures.P.tenuegrew well in the pfesence of 1: 1 chelates (molar ratio of chelator to Fe) of CyDTA, DTPA, EDDHA and HBED as wellas EDTA as the iron sources.P. tenuegrew well in the presenceof CyDTA up to 17-fold for Fe (molar ratio) . However, the growth ofP.tenuewas suppressed in the presence of DTPA of 7-fold, EDDHA of 3-fold and HBED of 3-fold for Fe (molar ratio), respectively.P.tenuealso could utilize FeII (BPDS) 3chelate as the iron source. In addition, it could utilize FeII (BPDS) 3in the presence of HBED. However, it could not utilize FeII (BPDS) 3in the presence of DTPA, DESF or EDDHA.The present results indicate thatP.tenuecan utilize a wide variety of iron chelates as the iron sources and has a stronger ability of chelating functions on the cell surfaces compared withO.tenuisandA. macrospora. However, the addition of excess of chelating agents (DTPA, DESF, EDDHA and HBED) having higher stability constants of Fe (III) chelates affected the growth ofP.tenue. Furthermore, the results show that the absorption of iron byP.tenuedoes not only depend on the stability constants of Fe chelates and that it also depends on the chemical structure or characteristics of chelators.