An<i>escherichia coli</i>bioassay of individual siderophores in soil

Nelson, Marjorie M.; Cooper, Chester R.; Crowley, David E.; Reid, C. P. P.; Szaniszlo, Paul J.

doi:10.1080/01904168809363856

Cited by 33 publications

(14 citation statements)

References 22 publications

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“…The results demonstrate the role of the apoplasmic Fe pool in roots for Fe nutrition particularly of Strategy II plants. Higher concentrations of siderophores in the rhizosphere soil as compared with the bulk soil (Nelson et al, 1988) might provide a mean to increase apoplast loading and thereby indirectly Fe acquisition of soil-grown plants.…”

Section: ) Iron Uptake From Microbial Siderophoresmentioning

confidence: 99%

Strategies of plants for acquisition of iron

1994

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Two different types of root response to Fe deficiency (strategies) have been identified in species of the Plant Kingdom. In Strategy I which occurs in all plant species except grasses, a plasma membrane-bound reductase is induced with enhanced net excretion of protons. Often the release of reductants/chelators is also higher. In Strategy II which is confined to grasses, there is an increase in the biosynthesis and secretion of phytosiderophores which form chelates with Fe It1. Uptake of Fe Iu phytosiderophores is mediated by a specific transporter in the plasma membrane of root cells of grasses. From results based mainly on long-term studies under non-axenic conditions this classification into two strategies has been questioned, and the utilization of Fe from microbial siderophores has been considered as an alternative strategy particularly in grasses. Possible reasons for controversial results are discussed in some detail. The numerous effects of microorganisms in non-axenic cultures, and the as yet inadequate characterization of the so-called standard (basic) reductase present major limitations to understanding different mechanisms of Fe acquisition. In comparison with the progress made in identifying the cellular mechanisms of root responses in Strategy I and Strategy II plants, our understanding is poor concerning the processes taking place in the apoplasm of root rhizodermal cells and of the role of low-molecular-weight root exudates and siderophores in Fe acquisition of plants growing in soils of differing Fe availability.

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Section: ) Iron Uptake From Microbial Siderophoresmentioning

confidence: 99%

Strategies of plants for acquisition of iron

1994

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“…These include, FepA for ferrienterobactin, Iut for ferric-aerobactin, FhuA, FhuE, and FhuF for the ferric-hydroxamate siderophores, ferrichrome, coprogen, and ferrioxamine, respectively, and FecA for ferricdicitrate (Braun et al, 1987;Nelson et al, 1988). After transport into the periplasm, subsequent transport of ferric-siderophores or ferric-dicitrate into the cytoplasm involves corresponding sets of cytoplasmic membrane proteins, including FepB, FepC, FepD, and FepG for ferrienterobactin, FecB, FecC, FecD, and FecE for ferric-dicitrate and three proteins designated FhuB, FhuC, and FhuD for ferric-hydroxamate siderophores.…”

Section: Generalized Mechanisms Of Fe Transport By Microorganismsmentioning

confidence: 99%

“…To determine which siderophores may be produced in the rhizosphere, we have developed bioassay procedures for quantification of different siderophore types (Nelson et al, 1988) and are now focusing on development of auxotrophic bacterial strains that can be used to detect various pyoverdin-type siderophores produced by Pseudomonas. Current procedures that involve water extraction of nonsterile soils are difficult to use quantitatively and have yielded very conservative data.…”

Section: Ecological and Soil Chemical Factors Affecting The Efficacy mentioning

confidence: 99%

Mechanisms of iron acquisition from siderophores by microorganisms and plants

et al. 1991

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Most bacteria, fungi, and some plants respond to Fe stress by the induction of high-affinity Fe transport systems that utilize biosynthetic chelates called siderophores. To competitively acquire Fe, some microbes have transport systems that enable them to use other siderophore types in addition to their own. Bacteria such as Escherichia coli achieve this ability by using a combination of separate siderophore receptors and transporters, whereas other microbial species, such as Streptomyces pilosus, use a low specificity, high-affinity transport system that recognizes more than one siderophore type. By either strategy, such versatility may provide an advantage under Fe-limiting conditions; allowing use of siderophores produced at another organism's expense, or Fe acquisition from siderophores that could otherwise sequester Fe in an unavailable form.Plants that use microbial siderophores may also be more Fe efficient by virtue of their ability to use a variety of Fe sources under different soil conditions. Results of our research examining Fe transport by oat indicate parity in plant and microbial requirements for Fe and suggest that siderophores produced by root-colonizing microbes may provide Fe to plants that can use the predominant siderophore types. In conjunction with transport mechanisms, ecological and soil chemical factors can influence the efficacy of siderophores and phytosiderophores. A model presented here attempts to incorporate these factors to predict conditions that may govern competition for Fe in the plant rhizosphere. Possibly such competition has been a factor in the evolution of broad transport capabilities for different siderophores by microorganisms and plants.

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“…Studies of marine systems have reported concentrations of strong iron complexing ligands between 0.3 and 7 nM (Gledhill and van den Berg, 1994;Gledhill et al, 1998;Powell and Donat, 2001;Rue and Bruland, 1997;van den Berg, 1995;Witter and Luther 1998;Wu and Luther, 1995). In soil solutions siderophore concentrations depend strongly on the soil horizons and higher concentrations occur in the rhizosphere compared to bulk soil (Bossier et al,1988 and references;Nelson et al, 1988). Also, field experiments with Pseudomonas fluorescens containing an iron-regulated promoter fused to an ice nucleation reporter gene showed that the production of siderophores is a function of soil pH in the rhizosphere as predicted from laboratory experiments (Loper and Henkels, 1997).…”

Section: Siderophore Concentrations In Natural Systemsmentioning

confidence: 99%

Iron oxide dissolution and solubility in the presence of siderophores

Kraemer

2004

Aquatic Sciences - Research Across Boundaries

537

386

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Abstract.Iron is an essential trace nutrient for most known organisms. The iron availability is limited by the solubility and the slow dissolution kinetics of iron-bearing mineral phases, particularly in pH neutral or alkaline environments such as carbonatic soils and ocean water. Bacteria, fungi, and plants have evolved iron acquisition systems to increase the bioavailability of iron in such environments. A particularly efficient iron acquisition system involves the solubilization of iron by siderophores. Siderophores are biogenic chelators with high affinity and specificity for iron complexation.This review focuses on the geochemical aspects of biological iron acquisition. The significance of iron-bearing minerals as nutrient source for siderophore-promoted iron Aquat. Sci. 66 (2004) Dübendorf, 2004 Aquatic Sciences acquisition has been confirmed in microbial culture studies. Due to the extraordinary thermodynamic stability of soluble siderophore-iron complexes, siderophores have a pronounced effect on the solubility of iron oxides over a wide pH range. Very small concentrations of free siderophores in solution have a large effect on the solution saturation state of iron oxides. This siderophore induced disequilibrium can drive dissolution mechanisms such as protonpromoted or ligand-promoted iron oxide dissolution. The adsorption of siderophores to oxide surfaces also induces a direct siderophore-promoted surface-controlled dissolution mechanism. The efficiency of siderophores for increasing the solubility and dissolution kinetics of iron oxides are compared to other natural and anthropogenic ligands.3-18 1015-1621/04/010003-16 DOI 10.1007/s00027-003-0690-5 © EAWAG,

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Anescherichia colibioassay of individual siderophores in soil

Cited by 33 publications

References 22 publications

Strategies of plants for acquisition of iron

Strategies of plants for acquisition of iron

Mechanisms of iron acquisition from siderophores by microorganisms and plants

Iron oxide dissolution and solubility in the presence of siderophores

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