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Escherichia coli response to uranyl exposure at low pH and associated protein regulations.

Khemiri A, Carrière M, Bremond N, Ben Mlouka MA, Coquet L, Llorens I, Chapon V, Jouenne T, Cosette P, Berthomieu C - PLoS ONE (2014)

Bottom Line: Additionally, this impact was analyzed by two-dimensional differential gel electrophoresis proteomics to discover protein actors specifically present or accumulated in contact with uranium.Exposure to uranium resulted in differential accumulation of proteins associated with oxidative stress and in the accumulation of the NADH/quinone oxidoreductase WrbA.This FMN dependent protein performs obligate two-electron reduction of quinones, and may be involved in cells response to oxidative stress.Interestingly, this WrbA protein presents similarities with the chromate reductase from E. coli, which was shown to reduce uranyl in vitro.

View Article: PubMed Central - PubMed

Affiliation: CEA, DSV, IBEB, Commissariat à l'Energie Atomique, Laboratoire des Interactions Protéine-Métal, Saint-Paul-lez-Durance, France ; CNRS, UMR Biologie Végétale et Microbiologie Environnementales 7265, Saint-Paul-lez-Durance, France ; Université d'Aix-Marseille, Saint-Paul-lez-Durance, France.

ABSTRACT
Better understanding of uranyl toxicity in bacteria is necessary to optimize strains for bioremediation purposes or for using bacteria as biodetectors for bioavailable uranyl. In this study, after different steps of optimization, Escherichia coli cells were exposed to uranyl at low pH to minimize uranyl precipitation and to increase its bioavailability. Bacteria were adapted to mid acidic pH before exposure to 50 or 80 µM uranyl acetate for two hours at pH≈3. To evaluate the impact of uranium, growth in these conditions were compared and the same rates of cells survival were observed in control and uranyl exposed cultures. Additionally, this impact was analyzed by two-dimensional differential gel electrophoresis proteomics to discover protein actors specifically present or accumulated in contact with uranium.Exposure to uranium resulted in differential accumulation of proteins associated with oxidative stress and in the accumulation of the NADH/quinone oxidoreductase WrbA. This FMN dependent protein performs obligate two-electron reduction of quinones, and may be involved in cells response to oxidative stress. Interestingly, this WrbA protein presents similarities with the chromate reductase from E. coli, which was shown to reduce uranyl in vitro.

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Uranium speciation in the exposure medium.Uranium LIII-edge XAS spectra (A), normalized to equal intensity at 17.176 keV; and k3-weighted EXAFS curves (B) of uranyl acetate 50 µM prepared in LB-glucose medium at pH 2.7 (U-LBG pH 2,7) compared to reference spectra.
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pone-0089863-g002: Uranium speciation in the exposure medium.Uranium LIII-edge XAS spectra (A), normalized to equal intensity at 17.176 keV; and k3-weighted EXAFS curves (B) of uranyl acetate 50 µM prepared in LB-glucose medium at pH 2.7 (U-LBG pH 2,7) compared to reference spectra.

Mentions: The speciation of uranyl in the exposure medium was analyzed using X-ray absorption spectroscopy (XAS) (Figure 2). This medium, dedicated to bacterial growth is mainly composed of proteins or amino acids, sugar moieties and salts. It contains phosphate residues, but the presence of strong uranyl ligands such as carbonate or citrate is unexpected. Consequently, uranyl may be found as complexes with phosphate, glucose, or carboxylate moieties of proteins and amino acids residues [37], [38]. Given the complexity of this medium, uranium speciation is suspected to be rather complex.


Escherichia coli response to uranyl exposure at low pH and associated protein regulations.

Khemiri A, Carrière M, Bremond N, Ben Mlouka MA, Coquet L, Llorens I, Chapon V, Jouenne T, Cosette P, Berthomieu C - PLoS ONE (2014)

Uranium speciation in the exposure medium.Uranium LIII-edge XAS spectra (A), normalized to equal intensity at 17.176 keV; and k3-weighted EXAFS curves (B) of uranyl acetate 50 µM prepared in LB-glucose medium at pH 2.7 (U-LBG pH 2,7) compared to reference spectra.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3935937&req=5

pone-0089863-g002: Uranium speciation in the exposure medium.Uranium LIII-edge XAS spectra (A), normalized to equal intensity at 17.176 keV; and k3-weighted EXAFS curves (B) of uranyl acetate 50 µM prepared in LB-glucose medium at pH 2.7 (U-LBG pH 2,7) compared to reference spectra.
Mentions: The speciation of uranyl in the exposure medium was analyzed using X-ray absorption spectroscopy (XAS) (Figure 2). This medium, dedicated to bacterial growth is mainly composed of proteins or amino acids, sugar moieties and salts. It contains phosphate residues, but the presence of strong uranyl ligands such as carbonate or citrate is unexpected. Consequently, uranyl may be found as complexes with phosphate, glucose, or carboxylate moieties of proteins and amino acids residues [37], [38]. Given the complexity of this medium, uranium speciation is suspected to be rather complex.

Bottom Line: Additionally, this impact was analyzed by two-dimensional differential gel electrophoresis proteomics to discover protein actors specifically present or accumulated in contact with uranium.Exposure to uranium resulted in differential accumulation of proteins associated with oxidative stress and in the accumulation of the NADH/quinone oxidoreductase WrbA.This FMN dependent protein performs obligate two-electron reduction of quinones, and may be involved in cells response to oxidative stress.Interestingly, this WrbA protein presents similarities with the chromate reductase from E. coli, which was shown to reduce uranyl in vitro.

View Article: PubMed Central - PubMed

Affiliation: CEA, DSV, IBEB, Commissariat à l'Energie Atomique, Laboratoire des Interactions Protéine-Métal, Saint-Paul-lez-Durance, France ; CNRS, UMR Biologie Végétale et Microbiologie Environnementales 7265, Saint-Paul-lez-Durance, France ; Université d'Aix-Marseille, Saint-Paul-lez-Durance, France.

ABSTRACT
Better understanding of uranyl toxicity in bacteria is necessary to optimize strains for bioremediation purposes or for using bacteria as biodetectors for bioavailable uranyl. In this study, after different steps of optimization, Escherichia coli cells were exposed to uranyl at low pH to minimize uranyl precipitation and to increase its bioavailability. Bacteria were adapted to mid acidic pH before exposure to 50 or 80 µM uranyl acetate for two hours at pH≈3. To evaluate the impact of uranium, growth in these conditions were compared and the same rates of cells survival were observed in control and uranyl exposed cultures. Additionally, this impact was analyzed by two-dimensional differential gel electrophoresis proteomics to discover protein actors specifically present or accumulated in contact with uranium.Exposure to uranium resulted in differential accumulation of proteins associated with oxidative stress and in the accumulation of the NADH/quinone oxidoreductase WrbA. This FMN dependent protein performs obligate two-electron reduction of quinones, and may be involved in cells response to oxidative stress. Interestingly, this WrbA protein presents similarities with the chromate reductase from E. coli, which was shown to reduce uranyl in vitro.

Show MeSH
Related in: MedlinePlus