es404186v_si_001.pdf (328.71 kB)
Accessibility of Humic-Associated Fe to a Microbial Siderophore: Implications for Bioavailability
journal contribution
posted on 2014-01-21, 00:00 authored by Keshia
M. Kuhn, Patricia A. Maurice, Elisabeth Neubauer, Thilo Hofmann, Frank von der KammerMicroorganisms 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 “transphilic”,
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–MS and UV–vis 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 “bridging” 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 “transphilic”
organic components therefore should be considered readily bioavailable
to aerobic, siderophore-producing microorganisms.