The fate of siderophores: antagonistic environmental interactions in exudate-mediated micronutrient uptake

Abstract

Organisms acquire metals from the environment by releasing small molecules that solubilize and promote their specific uptake. The best known example of this nutrient uptake strategy is the exudation of siderophores, which are a structurally-diverse class of molecules that are traditionally viewed as being integral to iron uptake. Siderophores have been proposed to act through a variety of processes, but their effectiveness can be mitigated by a variety of chemical and physical processes of both biotic and abiotic origin. Processes that occur at the surface of minerals can degrade or sequester siderophores, preventing them from fulfilling their function of returning metals to the organism. In addition, biotic processes including enzymatic degradation of the siderophore and piracy of the metal or of the siderophore complex also disrupt iron uptake. Some organisms have adapted their nutrient acquisition strategies to address these potential pitfalls, producing multiple siderophores and other exudates that take advantage of varying kinetic and thermodynamic factors to allow the continued uptake of metals. A complete understanding of the factors that contribute to metal uptake in nature will require a concerted effort to study processes identified in laboratory systems in the context of more complicated environmental systems.

Promising bacterial genera for agricultural practices: An insight on plant growth-promoting properties and microbial safety aspects

“…Laboratory studies have shown that hydrolyze products from coprogen (tri-hydroxamate siderophore) were also effective iron-carriers to cucumber and maize plants (Hördt et al, 2000). All these facts evidence a possible strategy for siderophore utilization where the presence of "sacrificial" moieties may help on the reduction, dissolution and transport of iron to (micro)organisms (Harrington et al, 2015).…”

“…In the environment, the majority of siderophore producers are confined to plant rhizosphere (Chauhan et al, 2015). For this reason, the siderophore concentration is maximum in the rhizosphere zone, where concentrations as high as 0.1 μmol•L −1 and 1 mmol•L −1 for bacterial siderophore and plant phytosiderophore, respectively, were reported (Harrington et al, 2015). Conversely, siderophore concentration drops dramatically from rhizosphere to bulk soil, where siderophore concentrations can be as low as 10 nmol•L −1 (Ahmed and Holmström, 2014b).…”

“…Conversely, siderophore concentration drops dramatically from rhizosphere to bulk soil, where siderophore concentrations can be as low as 10 nmol•L −1 (Ahmed and Holmström, 2014b). However, these values may be underestimated due to sorption phenomena and inadequate extraction and detection protocols for siderophore quantification (Harrington et al, 2015). In fact, in soil, siderophores may adsorb to clay minerals (oxyhydr)oxides and organic matter (Powell et al, 1982).…”

Saline and Arid Soils: Impact on Bacteria, Plants, and Their Interaction

“…Microorganisms able to synthesize siderophores are present in a large amount in the rhizosphere [ 68 ]. As a consequence, the siderophore concentration is maximum in the rhizosphere, where it reaches 0.1 μmol·L −1 and 1 mmol·L −1 for bacterial and plant siderophore, respectively [ 69 ], while a very low level is found in bulk soil (10 nmol·L −1 ) [ 70 ]. Among rhizobacteria, the use of homologous siderophores, produced by members of the same genus, is very common, while the use of heterologous ones, synthesized by bacteria belonging to different genera, is also possible [ 71 ].…”

Spatio-temporal Responses of Arabidopsis Leaves in Photosynthetic Performance and Metabolite Contents to Burkholderia phytofirmans PsJN

“…Hacihaliloglu ) increased nutrient element composition (N, P, K, Ca, and Mg) and also chlorophyll contents ( Esitken et al, 2003 ). Moreover, siderophores produced by bacteria chelate iron and make it available to the plant ( Harrington et al, 2015 ). In plants, iron is involved in the synthesis of chlorophyll, thylakoids, and chloroplasts ( Miller et al, 1995 ).…”