Accessibility of Humic-Associated Fe to a Microbial Siderophore: Implications for Bioavailability

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• 作者：Keshia M. Kuhn ; Patricia A. Maurice ; Elisabeth Neubauer ; Thilo Hofmann ; Frank von der Kammer
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：January 21, 2014
• 年：2014
• 卷：48
• 期：2
• 页码：1015-1022
• 全文大小：359K
• ISSN：1520-5851

文摘

Microorganisms in aerobic, circum-neutral environments are challenged to acquire sufficient nutrient Fe due to low solubilities of Fe oxides. To overcome this challenge, many aerobic microbes produce low molecular weight (MW) organic ligands, or siderophores, with extremely high Fe-binding affinities. This research expands the existing understanding of siderophore-mediated Fe acquisition from minerals by examining the effects of the siderophore desferrioxamine B (DFOB) on Fe removal from aquatic humic substances (XAD-8-isolated) and other organic matter (OM) isolates (reverse osmosis, RO; and 鈥渢ransphilic鈥? XAD-4) from several rivers including the Suwannee River (GA, USA). Analysis of samples by asymmetrical flow field-flow fractionation (AsFlFFF) with in-line ICP鈥揗S and UV鈥搗is detectors showed that Fe was naturally abundant and primarily associated with intermediate to high MW OM. An excess of DFOB (relative to naturally present Fe) removed 75% of Fe and shifted the OM MW distribution to lower MWs, perhaps due to removal of 鈥渂ridging鈥?Fe, although additional mechanistic study of MW shifts is needed. Removal of other OM-associated metals (e.g., Al, Cu, Zn) by DFOB was minimal for all but a few samples. Fe bound to humic substances and other more 鈥渢ransphilic鈥?organic components therefore should be considered readily bioavailable to aerobic, siderophore-producing microorganisms.