School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
Environ Sci Technol. 2010 Mar 15;44(6):1980-6. doi: 10.1021/es901315a.
We have investigated the mechanism of Fe uptake by a toxic strain of the freshwater cyanobacterium Microcystis aeruginosa (PCC7806) with particular attention given to the effect of Fe(II) and Fe(III) transformation kinetics on Fe uptake. Chemiluminescence analysis revealed that M. aeruginosa produces extracellular superoxide (a moderate Fe reducing agent) at rates of 0.4-1.2 amol cell(-1) h(-1) depending on initial Fe concentration in the culture medium. Short-term assimilation assays using (55)Fe showed that reduction of Fe(III) in both organic and inorganic forms by cell-generated superoxide or ascorbate facilitated Fe uptake via formation of unchelated Fe(II), when Fe availability was low because of the use of the strong Fe chelator ethylenediaminetetraacetate (EDTA) as a ligand. In contrast, Fe reduction was unimportant for Fe uptake in the presence of low concentrations (< or =100 microM) of the weak Fe-binding ligand citrate because of a high concentration of unchelated Fe(III), indicating that the contribution of reduction to Fe uptake depends on the nature of Fe binding and availability of unchelated Fe(III) in the external medium. A kinetic model incorporating uptake of both unchelated Fe(II) and Fe(III) and based on similar models developed for marine microalgae successfully described Fe uptake rates by M. aeruginosa PCC7806.
我们研究了淡水蓝藻铜绿微囊藻（PCC7806）的一种有毒菌株摄取铁的机制，特别关注铁（II）和铁（III）转化动力学对铁摄取的影响。化学发光分析显示，铜绿微囊藻以 0.4-1.2 amol 细胞（-1）h（-1）的速率产生细胞外超氧阴离子（一种中等强度的铁还原剂），这取决于培养基中初始铁浓度。使用（55）Fe 的短期同化测定表明，细胞产生的超氧阴离子或抗坏血酸还原有机和无机形式的铁（III），通过形成未配位的 Fe（II），促进了铁的摄取，因为使用了强铁螯合剂乙二胺四乙酸（EDTA）作为配体，导致铁的可用性较低。相比之下，由于外部介质中存在高浓度的未配位铁（III），弱铁结合配体柠檬酸盐（浓度低于或等于 100 microM）的存在时，铁还原对铁摄取不重要，这表明还原对铁摄取的贡献取决于铁结合的性质和外部介质中未配位铁（III）的可用性。一个包含未配位的 Fe（II）和 Fe（III）摄取的动力学模型，基于为海洋微藻开发的类似模型，成功地描述了铜绿微囊藻 PCC7806 的铁摄取速率。
