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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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Schematic view of E. coli cells exposure to uranium and details of the optimized analysis protocol.
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pone-0089863-g001: Schematic view of E. coli cells exposure to uranium and details of the optimized analysis protocol.

Mentions: In this study, we took advantage of the acid resistance property of E. coli to characterize the E. coli K-12 strain MG1655after uranium 238 (238U) exposure in LB (1/10)-glucose medium at pH 2.7 (Figure 1). These experimental conditions of exposure were chosen mainly for two reasons. First, the pH was fixed below pH 4 and the LB medium diluted tenfold to minimize the level of complexation between uranyl and phosphate orcarbonate groups. In addition, diluted LB supplemented with glucose was chosen for the presence of various amino acids and organic molecules since this may reduce the level of stress engendered by the hostile growth conditions (i.e. low pH anduranyl exposure). Second, E. coli has been used in basic research as a model organism for a long time. Physiology and genetics of this bacterium are among the best characterized of all species. Accordingly, the activity of its encoded proteins is probably at the best level of understanding in bacteria.


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)

Schematic view of E. coli cells exposure to uranium and details of the optimized analysis protocol.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0089863-g001: Schematic view of E. coli cells exposure to uranium and details of the optimized analysis protocol.
Mentions: In this study, we took advantage of the acid resistance property of E. coli to characterize the E. coli K-12 strain MG1655after uranium 238 (238U) exposure in LB (1/10)-glucose medium at pH 2.7 (Figure 1). These experimental conditions of exposure were chosen mainly for two reasons. First, the pH was fixed below pH 4 and the LB medium diluted tenfold to minimize the level of complexation between uranyl and phosphate orcarbonate groups. In addition, diluted LB supplemented with glucose was chosen for the presence of various amino acids and organic molecules since this may reduce the level of stress engendered by the hostile growth conditions (i.e. low pH anduranyl exposure). Second, E. coli has been used in basic research as a model organism for a long time. Physiology and genetics of this bacterium are among the best characterized of all species. Accordingly, the activity of its encoded proteins is probably at the best level of understanding in bacteria.

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