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Siderophore-Mediated Iron Dissolution from Nontronites Is Controlled by Mineral Cristallochemistry.

Parrello D, Zegeye A, Mustin C, Billard P - Front Microbiol (2016)

Bottom Line: Both nontronites released Fe in a particle concentration-dependent manner when incubated with the wild-type P. aeruginosa strain, however iron released from NAu-2 was substantially greater than from NAu-1.The structural Fe present on the edges of NAu-2 rather than NAu-1 particles appears to be more bio-accessible, indicating that the distribution of Fe, in the tetrahedron and/or in the octahedron sites, governs the solubilisation process.Furthermore, we also revealed that P. aeruginosa could acquire iron when in direct contact with mineral particles in a siderophore-independent manner.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360 Centre National de la Recherche Scientifique - Université de LorraineVandœuvre-lès-Nancy, France; Civil and Environmental Engineering, University of MissouriColumbia, MO, USA.

ABSTRACT
Bacteria living in oxic environments experience iron deficiency due to limited solubility and slow dissolution kinetics of iron-bearing minerals. To cope with iron deprivation, aerobic bacteria have evolved various strategies, including release of siderophores or other organic acids that scavenge external Fe(III) and deliver it to the cells. This research investigated the role of siderophores produced by Pseudomonas aeruginosa in the acquisition of Fe(III) from two iron-bearing colloidal nontronites (NAu-1 and NAu-2), comparing differences in bioavailability related with site occupancy and distribution of Fe(III) in the two lattices. To avoid both the direct contact of the mineral colloids with the bacterial cells and the uncontrolled particle aggregation, nontronite suspensions were homogenously dispersed in a porous silica gel before the dissolution experiments. A multiparametric approach coupling UV-vis spectroscopy and spectral decomposition algorithm was implemented to monitor simultaneously the solubilisation of Fe and the production of pyoverdine in microplate-based batch experiments. Both nontronites released Fe in a particle concentration-dependent manner when incubated with the wild-type P. aeruginosa strain, however iron released from NAu-2 was substantially greater than from NAu-1. The profile of organic acids produced in both cases was similar and may not account for the difference in the iron dissolution efficiency. In contrast, a pyoverdine-deficient mutant was unable to mobilize Fe(III) from either nontronite, whereas iron dissolution occurred in abiotic experiments conducted with purified pyoverdine. Overall, our data provide evidence that P. aeruginosa indirectly mobilize Fe from nontronites primarily through the production of pyoverdine. The structural Fe present on the edges of NAu-2 rather than NAu-1 particles appears to be more bio-accessible, indicating that the distribution of Fe, in the tetrahedron and/or in the octahedron sites, governs the solubilisation process. Furthermore, we also revealed that P. aeruginosa could acquire iron when in direct contact with mineral particles in a siderophore-independent manner.

No MeSH data available.


Related in: MedlinePlus

Pyoverdine-mediated iron release from NAu-2. Silica gel embedded NAu-2 particles were incubated with or without purified pyoverdine (PVD) and with cell-free culture supernatants of PAO1 WT, PAO1 ΔpvdA or PAO1 ΔpvdD ΔpchEF strains grown in DCAA medium. Pyoverdine and iron concentrations were determined after 24 h of incubation. Errors bars represent the standard error of the mean (n = 3).
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Figure 5: Pyoverdine-mediated iron release from NAu-2. Silica gel embedded NAu-2 particles were incubated with or without purified pyoverdine (PVD) and with cell-free culture supernatants of PAO1 WT, PAO1 ΔpvdA or PAO1 ΔpvdD ΔpchEF strains grown in DCAA medium. Pyoverdine and iron concentrations were determined after 24 h of incubation. Errors bars represent the standard error of the mean (n = 3).

Mentions: To further investigate the role of pyoverdine in the mobilization of iron from nontronite, we performed batch experiments where silica gel plugs containing NAu-2 were incubated in iron deficient DCAA medium supplemented with purified pyoverdine, as well as in cell-free culture supernatants of PAO1 WT grown in DCAA. The analysis of the assay media after 24 h of incubation revealed that iron was mobilized in both cases (Figure 5). Comparable initial concentrations of pyoverdine in the assays led to the same level of iron dissolution, indicating that organic acids, pyochelin or other metabolite in the culture supernatant did not significantly contribute to mineral weathering. This was confirmed by the absence of detectable iron in assays performed with culture supernatants of the pyoverdin deficient mutant PAO1 ΔpvdD and the double pyochelin- and pyoverdine-deficient mutant (PAO1 ΔpvdD ΔpchEF). Overall, these data unambiguously show that pyoverdine is the main agent involved in weathering of nontronite in the absence of physical contact with bacterial cells.


Siderophore-Mediated Iron Dissolution from Nontronites Is Controlled by Mineral Cristallochemistry.

Parrello D, Zegeye A, Mustin C, Billard P - Front Microbiol (2016)

Pyoverdine-mediated iron release from NAu-2. Silica gel embedded NAu-2 particles were incubated with or without purified pyoverdine (PVD) and with cell-free culture supernatants of PAO1 WT, PAO1 ΔpvdA or PAO1 ΔpvdD ΔpchEF strains grown in DCAA medium. Pyoverdine and iron concentrations were determined after 24 h of incubation. Errors bars represent the standard error of the mean (n = 3).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4814481&req=5

Figure 5: Pyoverdine-mediated iron release from NAu-2. Silica gel embedded NAu-2 particles were incubated with or without purified pyoverdine (PVD) and with cell-free culture supernatants of PAO1 WT, PAO1 ΔpvdA or PAO1 ΔpvdD ΔpchEF strains grown in DCAA medium. Pyoverdine and iron concentrations were determined after 24 h of incubation. Errors bars represent the standard error of the mean (n = 3).
Mentions: To further investigate the role of pyoverdine in the mobilization of iron from nontronite, we performed batch experiments where silica gel plugs containing NAu-2 were incubated in iron deficient DCAA medium supplemented with purified pyoverdine, as well as in cell-free culture supernatants of PAO1 WT grown in DCAA. The analysis of the assay media after 24 h of incubation revealed that iron was mobilized in both cases (Figure 5). Comparable initial concentrations of pyoverdine in the assays led to the same level of iron dissolution, indicating that organic acids, pyochelin or other metabolite in the culture supernatant did not significantly contribute to mineral weathering. This was confirmed by the absence of detectable iron in assays performed with culture supernatants of the pyoverdin deficient mutant PAO1 ΔpvdD and the double pyochelin- and pyoverdine-deficient mutant (PAO1 ΔpvdD ΔpchEF). Overall, these data unambiguously show that pyoverdine is the main agent involved in weathering of nontronite in the absence of physical contact with bacterial cells.

Bottom Line: Both nontronites released Fe in a particle concentration-dependent manner when incubated with the wild-type P. aeruginosa strain, however iron released from NAu-2 was substantially greater than from NAu-1.The structural Fe present on the edges of NAu-2 rather than NAu-1 particles appears to be more bio-accessible, indicating that the distribution of Fe, in the tetrahedron and/or in the octahedron sites, governs the solubilisation process.Furthermore, we also revealed that P. aeruginosa could acquire iron when in direct contact with mineral particles in a siderophore-independent manner.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360 Centre National de la Recherche Scientifique - Université de LorraineVandœuvre-lès-Nancy, France; Civil and Environmental Engineering, University of MissouriColumbia, MO, USA.

ABSTRACT
Bacteria living in oxic environments experience iron deficiency due to limited solubility and slow dissolution kinetics of iron-bearing minerals. To cope with iron deprivation, aerobic bacteria have evolved various strategies, including release of siderophores or other organic acids that scavenge external Fe(III) and deliver it to the cells. This research investigated the role of siderophores produced by Pseudomonas aeruginosa in the acquisition of Fe(III) from two iron-bearing colloidal nontronites (NAu-1 and NAu-2), comparing differences in bioavailability related with site occupancy and distribution of Fe(III) in the two lattices. To avoid both the direct contact of the mineral colloids with the bacterial cells and the uncontrolled particle aggregation, nontronite suspensions were homogenously dispersed in a porous silica gel before the dissolution experiments. A multiparametric approach coupling UV-vis spectroscopy and spectral decomposition algorithm was implemented to monitor simultaneously the solubilisation of Fe and the production of pyoverdine in microplate-based batch experiments. Both nontronites released Fe in a particle concentration-dependent manner when incubated with the wild-type P. aeruginosa strain, however iron released from NAu-2 was substantially greater than from NAu-1. The profile of organic acids produced in both cases was similar and may not account for the difference in the iron dissolution efficiency. In contrast, a pyoverdine-deficient mutant was unable to mobilize Fe(III) from either nontronite, whereas iron dissolution occurred in abiotic experiments conducted with purified pyoverdine. Overall, our data provide evidence that P. aeruginosa indirectly mobilize Fe from nontronites primarily through the production of pyoverdine. The structural Fe present on the edges of NAu-2 rather than NAu-1 particles appears to be more bio-accessible, indicating that the distribution of Fe, in the tetrahedron and/or in the octahedron sites, governs the solubilisation process. Furthermore, we also revealed that P. aeruginosa could acquire iron when in direct contact with mineral particles in a siderophore-independent manner.

No MeSH data available.


Related in: MedlinePlus