Siderophores and the Dissolution of Iron-Bearing Minerals in Marine Systems

Kraemer, Stephan M.; Butler, Alison; Borer, Paul; Cervini-Silva, Javiera

doi:10.2138/rmg.2005.59.4

Cited by 90 publications

(73 citation statements)

References 210 publications

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“…Because siderophores are small organic compounds (Butler and Theisen, 2010) able to solubilize colloidal Fe bearing minerals including oxyhydroxides (Kraemer et al, 2005), they are thus expected to be found in the soluble phase. However, soluble ligands show a lower conditional stability constant for iron binding than colloidal ligands (Boye et al, 2010), thus contradicting the hypothesis that siderophores are mainly present in the soluble phase.…”

Section: A Putative Role For Exopolymeric Substances In Size Distribumentioning

confidence: 99%

“…This exchangeable pool is often referred to as the dissolved iron pool (Gledhill and Buck, 2012), a possibly misleading assumption as not all the dissolved iron might be exchangeable and as particulate iron can also react with organic ligands such as siderophores and HS (Kraemer et al, 2005;Paris and Desboeufs, 2013;Fishwick et al, 2014). It is also to be noted that the co-existence of multiple metals has implications for iron biogeochemistry as organic ligands may bind metals with different binding affinities, potentially leading to competition, representing a research direction mostly unexplored for in-situ oceanic ligands.…”

Section: Implications Of the Co-existence Of Iron-binding Ligandsmentioning

confidence: 99%

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Toward a Regional Classification to Provide a More Inclusive Examination of the Ocean Biogeochemistry of Iron-Binding Ligands

2017

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Iron-binding ligands are paramount to understanding iron biogeochemistry and its potential to set the productivity and the magnitude of the biological pump in >30% of the ocean. However, the nature of these ligands is largely uncharacterized and little is known about their sources, sensitivity to photochemistry and biological transformation, or scavenging behavior. Despite many uncertainties, there is no doubt that ligands are produced by a wide range of biotic and abiotic processes, and that the bulk ligand pool encompasses a diverse range of molecules. Despite widespread recognition of the likelihood of a continuum of ligand classes making up the bulk ligand pool, studies to date largely focused on the dominant ligand. Thus, most studies have overlooked the need to assess where these targeted molecules fit across the spectrum of ligands that comprise the bulk ligand pool. Here we summarize present knowledge to critically assess the source(s), function(s), production pathways, and loss mechanisms of three important iron-binding organic ligand groups in order to assess their distinctive characteristics and how they link with observed ligand distributions. We considered that ligands are contained in broad groupings of exopolymer substances (EPS), humic substances (HS), and siderophores; using literature data for speciation modeling suggested that this adequately described the iron speciation reported in the ocean. We hypothesize that a holistic viewpoint of the multi-faceted controls on ligands dynamics is essential to begin to understand why some ligands can be expected to dominate in particular oceanic regions, depth strata, or exhibit seasonality and/or lateral gradients. We advocate that the development of a regional classification will enhance our understanding of the changing composition of the bulk ligand pool across the global ocean and to help address to what extent seasonality influences the makeup of this pool. This classification, based on selected functional ligand classes, can act as a bridge to use future ligand datasets to fill in the gaps in the continuum.

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Section: A Putative Role For Exopolymeric Substances In Size Distribumentioning

confidence: 99%

Section: Implications Of the Co-existence Of Iron-binding Ligandsmentioning

confidence: 99%

Toward a Regional Classification to Provide a More Inclusive Examination of the Ocean Biogeochemistry of Iron-Binding Ligands

2017

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“…Thermodynamically, siderophores are very capable of dissolving Fe(III) (hydr)oxides; however, the rate of in vitro dissolution is much slower than the in vivo microbial Fe uptake rate (5)(6)(7). In the presence of a reducing agent, siderophores have been shown to dissolve Fe(III) (hydr)oxides at a faster rate (1,9,12). This increased dissolution resulting from a combined effect of siderophore and reductant could potentially be the mechanism that suffices for the microbial demand for Fe (7).…”

mentioning

confidence: 99%

Effect of Exogenous Reductant on Growth and Iron Mobilization from Ferrihydrite by the Pseudomonas mendocina ymp Strain

Dhungana

Anthony

Hersman

2007

Appl Environ Microbiol

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Growth of the Pseudomonas mendocina ymp strain on insoluble ferrihydrite is enhanced by exogenous reductants with concurrent increase in soluble iron concentrations. This shows that exogenous reductants play a substantial role in the overall microbial iron bioavailability. The exogenous reductants may work together with the siderophores, Fe-scavenging agents, to facilitate ferrihydrite dissolution.

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“…In response to the scarcity of bioavailable iron in many natural environments, many microorganisms have, for example, evolved the ability to synthesize potent chelating agents to aid in iron acquisition. The fascinating and complex process of mobilization and acquisition of iron by these iron-specific chelators, commonly known as siderophores, is discussed in detail by Kraemer (2004) and Kraemer et al (2005).…”

Section: Iron As a Nutrientmentioning

confidence: 99%