Авторы: Hassler C., Twiss M.

2006 г.

Env.Sci.Techn.

    This study describes a short-term (12 h) evaluation of iron (Fe) bioavailability to an Fe-dependent cyanobacterial bioreporter derived from Synechococcus PCC 7942. Several synthetic ligands with variable conditional stability constants for Fe(III) (K* of 1019.8 to 1030.9), in addition to several defined natural Fe-binding ligands and a fulvic acid of aquatic origin (Suwannee River), were used to elucidate the forms of Fe that are discerned by this phytoplanktonic microbe: Fe-HEBD (log conditional stability constant, K*, ) 28.1, HEBD )N,N¢-di(2-hydroxybenzyl)ethylenediamine- N,N¢-diacetic acid monohydrochloride hydrate), Fe-HDFB (K* ) 30.9, DFB ) desferroxamine B), Fe-ferrichrome (K* ) 23.2), Fe-DTPA (K* ) 21.1, DTPA ) diethylenetrinitrilopentaacetic acid), Fe-(8HQS)2 (K* ) 20.4, 8HQS ) 8-hydroxyquinoline-5-sulfonic acid), Fe-CDTA (K* ) 19.8, CDTA ) trans-1,2-cyclohexylenedinitrilotetraacetic acid), and Fe-EDTA (K* ) 19.2). Iron bioavailability sensed by the bioreporter was related to diffusion limitation and activity of high-affinity transporters rather than by siderophore secretion. Iron complexed with a K* < 23.2 contributes to the bioavailable pool; bioavailability could be explained by disjunctive ligand exchange considerations and fully, partially, and nonbioavailable complexes could be distinguished according to their conditional stability constant. The use of Fe-bioreporters provides a relevant measurement of bioavailability to an important group of primary producers in freshwaters (cyanobacteria) and is thus a promising technique for understanding Fe cycling in aquatic systems.

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