Siderophore-promoted dissolution of hematite

Section: Discussionmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 99%

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Roles of Siderophores, Oxalate, and Ascorbate in Mobilization of Iron from Hematite by the Aerobic Bacterium Pseudomonas mendocina

Dehner

Awaya

Maurice

et al. 2010

“…Ingenious mechanisms to access iron have been developed by bacteria, the most well known of which is the use of siderophores, small iron-binding organic compounds, excreted to scavenge iron (39). Capable of binding various forms of iron, siderophores serve as a general iron acquisition pathway and are employed by bacteria from the human body, where free iron is limited to impede microbial growth, to soils, where iron is abundant but present in inert mineral phases of limited bioavailability (11,21). However, bacteria also have the ability to directly internalize forms of iron which are abundant in their environment, most notably heme, which is a large pool of iron in organisms and represents a major source of iron for mammalian pathogens (15,45) and may also be important for some symbiotic bacteria (40).…”

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confidence: 99%

Heme Uptake by Microscilla marina and Evidence for Heme Uptake Systems in the Genomes of Diverse Marine Bacteria

Hopkinson

Roe

Barbeau

2008

The ability to acquire diverse and abundant forms of iron would be expected to confer a survival advantage in the marine environment, where iron is scarce. Marine bacteria are known to use siderophores and inorganic iron, but their ability to use heme, an abundant intracellular iron form, has only been examined preliminarily. Microscilla marina, a cultured relative of a bacterial group frequently found on marine particulates, was used as a model organism to examine heme uptake. Searches of the genome revealed analogs to known heme transport proteins, and reverse transcription-quantitative PCR analysis of these genes showed that they were expressed and upregulated under iron stress and during growth on heme. M. marina was found to take up heme-bound iron and could grow on heme as a sole iron source, supporting the genetic evidence for heme transport. Similar putative heme transport components were identified in the genomes of diverse marine bacteria. These systems were found in the genomes of many bacteria thought to be particle associated but were lacking in known free-living organisms (e.g., Pelagibacter ubique and marine cyanobacteria). This distribution of transporters is consistent with the hydrophobic, light-sensitive nature of heme, suggesting that it is primarily available on phytoplankton or detritus or in nutrient-rich environments.

“…Microorganisms sense environmental Fe deficiency and produce low-molecular-weight Fechelating agents, siderophores, to solubilize Fe(III) (hydr)oxides and transport Fe into cells (2,5,15). Siderophores bind Fe 3ϩ with extremely high affinity, and this high formation constant between siderophore and Fe 3ϩ is believed to be the driving force that facilitates the dissolution of Fe(III) (hydr)oxides (3,5,8). 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).…”

mentioning

confidence: 99%

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

Dhungana

Anthony

Hersman

2007

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.