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The Role of the Two-Component System BaeSR in Disposing Chemicals through Regulating Transporter Systems in Acinetobacter baumannii.

Lin MF, Lin YY, Lan CY - PLoS ONE (2015)

Bottom Line: In this study, we demonstrate that an additional two transport systems, AdeIJK and MacAB-TolC, are also regulated by BaeSR.In the wild type and clinical tigecycline-resistant A. baumannii strains, gene expression of AdeIJK and MacAB-TolC increased after tigecycline induction, implicating their importance to tigecycline resistance in addition to AdeABC.In conclusion, A. baumannii can use the TCS BaeSR in disposing chemicals, such as tannic acid and tigecycline, through regulating the efflux pumps.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, National Taiwan University Hospital Chu-Tung Branch, Hsin-Chu City, Taiwan; Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan.

ABSTRACT
Bacterial two-component regulatory systems (TCSs) facilitate changes in gene expression in response to environmental stimuli. TCS BaeR regulons influence tigecycline susceptibility in Acinetobacter baumannii through positively regulating the pump genes adeA and adeB. In this study, we demonstrate that an additional two transport systems, AdeIJK and MacAB-TolC, are also regulated by BaeSR. In the wild type and clinical tigecycline-resistant A. baumannii strains, gene expression of AdeIJK and MacAB-TolC increased after tigecycline induction, implicating their importance to tigecycline resistance in addition to AdeABC. Phenotypic microarray results showed that A. baumannii is vulnerable to certain chemicals, especially tannic acid, after deleting baeR, which was confirmed using the spot assay. The wild-type strain of A. baumannii also exhibited 1.6-fold and 4.4-fold increase in gene expression of adeJ and macB in the medium with 100 μg/mL tannic acid, but the increase was fully inhibited by baeR deletion. An electrophoretic motility shift assay based on an interaction between His-BaeR and the adeA, adeI and macA promoter regions did not demonstrate direct binding. In conclusion, A. baumannii can use the TCS BaeSR in disposing chemicals, such as tannic acid and tigecycline, through regulating the efflux pumps.

No MeSH data available.


Related in: MedlinePlus

Spot assays and gene expression analyses after tannic acid exposure.(A) Spot assay. The wild-type strain exhibited better tolerance to tannic acid than the baeR mutant strain. (B) The gene expression levels of the baeR and pump genes in the wild-type strain. At 50 μg/mL tannic acid, only macB showed a statistically significant increase in the wild-type strain. Through increasing medium tannic acid up to 100 μg/mL, baeR, adeJ and macB exhibited increased gene expression. If the medium contained tannic acid 500 μg/mL, the expression of each gene investigated in the wild-type strain increased dramatically. (C) The gene expression levels of the pump genes in the baeR mutant strain. The gene expression of adeB, adeJ, and macB in the baeR mutant strain increased significantly at the tannic acid concentration 50 μg/mL. Through increasing the tannic acid concentration to 100 μg/mL, expression of each gene decreased to levels without tannic acid exposure. (D) The gene expression levels of the baeR and pump genes in the clinical strain ABhl1. The gene expression of baeR, adeB, and macB demonstrated a statistically significant increase upon being exposed to 100 and 500 μg/mL tannic acid. The results are shown as the means ± SD from three independent experiments. *, P < 0.05 and, **, P < 0.01 and ***, P < 0.001.
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pone.0132843.g004: Spot assays and gene expression analyses after tannic acid exposure.(A) Spot assay. The wild-type strain exhibited better tolerance to tannic acid than the baeR mutant strain. (B) The gene expression levels of the baeR and pump genes in the wild-type strain. At 50 μg/mL tannic acid, only macB showed a statistically significant increase in the wild-type strain. Through increasing medium tannic acid up to 100 μg/mL, baeR, adeJ and macB exhibited increased gene expression. If the medium contained tannic acid 500 μg/mL, the expression of each gene investigated in the wild-type strain increased dramatically. (C) The gene expression levels of the pump genes in the baeR mutant strain. The gene expression of adeB, adeJ, and macB in the baeR mutant strain increased significantly at the tannic acid concentration 50 μg/mL. Through increasing the tannic acid concentration to 100 μg/mL, expression of each gene decreased to levels without tannic acid exposure. (D) The gene expression levels of the baeR and pump genes in the clinical strain ABhl1. The gene expression of baeR, adeB, and macB demonstrated a statistically significant increase upon being exposed to 100 and 500 μg/mL tannic acid. The results are shown as the means ± SD from three independent experiments. *, P < 0.05 and, **, P < 0.01 and ***, P < 0.001.

Mentions: The ATCC 17978 strain can tolerate tannic acid as high as 250 μg/mL (Fig 4A). However, we did not observe growth of 20 μL 103 cells/mL baeR mutant bacterial solution in the LB plate containing 50 μg/mL tannic acid, whereas 100 μg/mL tannic acid fully inhibited 104 cells/mL baeR mutant strain. In the presence of 150 μg/mL tannic acid, no diluted bacterial solutions exhibited growth, except 107 cells/mL baeR mutant strain, which exhibited slight growth With an increasing tannic acid concentration, none of the studied bacterial baeR mutant strain solutions grew.


The Role of the Two-Component System BaeSR in Disposing Chemicals through Regulating Transporter Systems in Acinetobacter baumannii.

Lin MF, Lin YY, Lan CY - PLoS ONE (2015)

Spot assays and gene expression analyses after tannic acid exposure.(A) Spot assay. The wild-type strain exhibited better tolerance to tannic acid than the baeR mutant strain. (B) The gene expression levels of the baeR and pump genes in the wild-type strain. At 50 μg/mL tannic acid, only macB showed a statistically significant increase in the wild-type strain. Through increasing medium tannic acid up to 100 μg/mL, baeR, adeJ and macB exhibited increased gene expression. If the medium contained tannic acid 500 μg/mL, the expression of each gene investigated in the wild-type strain increased dramatically. (C) The gene expression levels of the pump genes in the baeR mutant strain. The gene expression of adeB, adeJ, and macB in the baeR mutant strain increased significantly at the tannic acid concentration 50 μg/mL. Through increasing the tannic acid concentration to 100 μg/mL, expression of each gene decreased to levels without tannic acid exposure. (D) The gene expression levels of the baeR and pump genes in the clinical strain ABhl1. The gene expression of baeR, adeB, and macB demonstrated a statistically significant increase upon being exposed to 100 and 500 μg/mL tannic acid. The results are shown as the means ± SD from three independent experiments. *, P < 0.05 and, **, P < 0.01 and ***, P < 0.001.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4498774&req=5

pone.0132843.g004: Spot assays and gene expression analyses after tannic acid exposure.(A) Spot assay. The wild-type strain exhibited better tolerance to tannic acid than the baeR mutant strain. (B) The gene expression levels of the baeR and pump genes in the wild-type strain. At 50 μg/mL tannic acid, only macB showed a statistically significant increase in the wild-type strain. Through increasing medium tannic acid up to 100 μg/mL, baeR, adeJ and macB exhibited increased gene expression. If the medium contained tannic acid 500 μg/mL, the expression of each gene investigated in the wild-type strain increased dramatically. (C) The gene expression levels of the pump genes in the baeR mutant strain. The gene expression of adeB, adeJ, and macB in the baeR mutant strain increased significantly at the tannic acid concentration 50 μg/mL. Through increasing the tannic acid concentration to 100 μg/mL, expression of each gene decreased to levels without tannic acid exposure. (D) The gene expression levels of the baeR and pump genes in the clinical strain ABhl1. The gene expression of baeR, adeB, and macB demonstrated a statistically significant increase upon being exposed to 100 and 500 μg/mL tannic acid. The results are shown as the means ± SD from three independent experiments. *, P < 0.05 and, **, P < 0.01 and ***, P < 0.001.
Mentions: The ATCC 17978 strain can tolerate tannic acid as high as 250 μg/mL (Fig 4A). However, we did not observe growth of 20 μL 103 cells/mL baeR mutant bacterial solution in the LB plate containing 50 μg/mL tannic acid, whereas 100 μg/mL tannic acid fully inhibited 104 cells/mL baeR mutant strain. In the presence of 150 μg/mL tannic acid, no diluted bacterial solutions exhibited growth, except 107 cells/mL baeR mutant strain, which exhibited slight growth With an increasing tannic acid concentration, none of the studied bacterial baeR mutant strain solutions grew.

Bottom Line: In this study, we demonstrate that an additional two transport systems, AdeIJK and MacAB-TolC, are also regulated by BaeSR.In the wild type and clinical tigecycline-resistant A. baumannii strains, gene expression of AdeIJK and MacAB-TolC increased after tigecycline induction, implicating their importance to tigecycline resistance in addition to AdeABC.In conclusion, A. baumannii can use the TCS BaeSR in disposing chemicals, such as tannic acid and tigecycline, through regulating the efflux pumps.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, National Taiwan University Hospital Chu-Tung Branch, Hsin-Chu City, Taiwan; Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan.

ABSTRACT
Bacterial two-component regulatory systems (TCSs) facilitate changes in gene expression in response to environmental stimuli. TCS BaeR regulons influence tigecycline susceptibility in Acinetobacter baumannii through positively regulating the pump genes adeA and adeB. In this study, we demonstrate that an additional two transport systems, AdeIJK and MacAB-TolC, are also regulated by BaeSR. In the wild type and clinical tigecycline-resistant A. baumannii strains, gene expression of AdeIJK and MacAB-TolC increased after tigecycline induction, implicating their importance to tigecycline resistance in addition to AdeABC. Phenotypic microarray results showed that A. baumannii is vulnerable to certain chemicals, especially tannic acid, after deleting baeR, which was confirmed using the spot assay. The wild-type strain of A. baumannii also exhibited 1.6-fold and 4.4-fold increase in gene expression of adeJ and macB in the medium with 100 μg/mL tannic acid, but the increase was fully inhibited by baeR deletion. An electrophoretic motility shift assay based on an interaction between His-BaeR and the adeA, adeI and macA promoter regions did not demonstrate direct binding. In conclusion, A. baumannii can use the TCS BaeSR in disposing chemicals, such as tannic acid and tigecycline, through regulating the efflux pumps.

No MeSH data available.


Related in: MedlinePlus