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Regulation of arsenite oxidation by the phosphate two-component system PhoBR in Halomonas sp. HAL1.

Chen F, Cao Y, Wei S, Li Y, Li X, Wang Q, Wang G - Front Microbiol (2015)

Bottom Line: HAL1.Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region.The new regulation model further implies the close metabolic connection between As and Pi.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University Wuhan, China.

ABSTRACT
Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR 931 and HAL1-▵phoB, were obtained in strain HAL1. The phoR and phoB constitute a two-component system which is responsible for phosphate (Pi) acquisition and assimilation. Both of the mutants showed negative As(III)-oxidation phenotypes in low Pi condition (0.1 mM) but not under normal Pi condition (1 mM). The phoBR complementation strain HAL1-▵phoB-C reversed the mutants' phenotypes back to wild type status. Meanwhile, lacZ reporter fusions using pCM-lacZ showed that the expression of phoBR and aioBA were both induced by As(III) but were not induced in HAL1-phoR 931 and HAL1-▵phoB. Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region. PhoB was able to bind to the putative Pho box in vivo (bacterial one-hybrid detection) and in vitro (electrophoretic mobility gel shift assay), and an 18-bp binding sequence containing nine conserved bases were determined. This study provided the evidence that PhoBR regulates the expression of aioBA in Halomonas sp. HAL1 under low Pi condition. The new regulation model further implies the close metabolic connection between As and Pi.

No MeSH data available.


Related in: MedlinePlus

As(III) oxidation was not influenced by phoBR in normal Pi condition. (A–D) The growth curves of strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C in MMNH4 medium with the presence of 1 mM Pi and 0.8 M NaCl, with or without the addition of 1 mM As(III). (E–H) As(III) oxidation profiles of the same strains. As(III) and As(V) concentrations in the cultural fluids were measured using HPLC-HG-AFS. Data symbols shown in (A) are the same for (B–D), and data symbols shown in (E) are the same for (F–H). Data are shown as the mean of three replicates, with the error bars illustrating one standard deviation.
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Figure 3: As(III) oxidation was not influenced by phoBR in normal Pi condition. (A–D) The growth curves of strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C in MMNH4 medium with the presence of 1 mM Pi and 0.8 M NaCl, with or without the addition of 1 mM As(III). (E–H) As(III) oxidation profiles of the same strains. As(III) and As(V) concentrations in the cultural fluids were measured using HPLC-HG-AFS. Data symbols shown in (A) are the same for (B–D), and data symbols shown in (E) are the same for (F–H). Data are shown as the mean of three replicates, with the error bars illustrating one standard deviation.

Mentions: The growth curves and As(III) oxidation efficiencies of the Halomonas sp. strains were tested in both low Pi (0.1 mM) and normal Pi (1 mM) conditions (Figures 2, 3). Consistent with the qualitative KMnO4 tests, the As(III) oxidation phenotypes disappeared at the low Pi condition in the phoR or phoB disruption strains, while the complemented strain HAL1-ΔphoB-C reversed the mutants phenotype back to wild type status (Figure 2). However, in the normal Pi condition, all of the four Halomonas sp. strains showed similar As(III) oxidation rates during the 7-day test (Figure 3), indicating that PhoBR may only have an effect on As(III) oxidation at the low Pi condition. The results are consistent with the properties of PhoBR because they are the regulators responsible for Pi stress (Hsieh and Wanner, 2010).


Regulation of arsenite oxidation by the phosphate two-component system PhoBR in Halomonas sp. HAL1.

Chen F, Cao Y, Wei S, Li Y, Li X, Wang Q, Wang G - Front Microbiol (2015)

As(III) oxidation was not influenced by phoBR in normal Pi condition. (A–D) The growth curves of strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C in MMNH4 medium with the presence of 1 mM Pi and 0.8 M NaCl, with or without the addition of 1 mM As(III). (E–H) As(III) oxidation profiles of the same strains. As(III) and As(V) concentrations in the cultural fluids were measured using HPLC-HG-AFS. Data symbols shown in (A) are the same for (B–D), and data symbols shown in (E) are the same for (F–H). Data are shown as the mean of three replicates, with the error bars illustrating one standard deviation.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4563254&req=5

Figure 3: As(III) oxidation was not influenced by phoBR in normal Pi condition. (A–D) The growth curves of strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C in MMNH4 medium with the presence of 1 mM Pi and 0.8 M NaCl, with or without the addition of 1 mM As(III). (E–H) As(III) oxidation profiles of the same strains. As(III) and As(V) concentrations in the cultural fluids were measured using HPLC-HG-AFS. Data symbols shown in (A) are the same for (B–D), and data symbols shown in (E) are the same for (F–H). Data are shown as the mean of three replicates, with the error bars illustrating one standard deviation.
Mentions: The growth curves and As(III) oxidation efficiencies of the Halomonas sp. strains were tested in both low Pi (0.1 mM) and normal Pi (1 mM) conditions (Figures 2, 3). Consistent with the qualitative KMnO4 tests, the As(III) oxidation phenotypes disappeared at the low Pi condition in the phoR or phoB disruption strains, while the complemented strain HAL1-ΔphoB-C reversed the mutants phenotype back to wild type status (Figure 2). However, in the normal Pi condition, all of the four Halomonas sp. strains showed similar As(III) oxidation rates during the 7-day test (Figure 3), indicating that PhoBR may only have an effect on As(III) oxidation at the low Pi condition. The results are consistent with the properties of PhoBR because they are the regulators responsible for Pi stress (Hsieh and Wanner, 2010).

Bottom Line: HAL1.Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region.The new regulation model further implies the close metabolic connection between As and Pi.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University Wuhan, China.

ABSTRACT
Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR 931 and HAL1-▵phoB, were obtained in strain HAL1. The phoR and phoB constitute a two-component system which is responsible for phosphate (Pi) acquisition and assimilation. Both of the mutants showed negative As(III)-oxidation phenotypes in low Pi condition (0.1 mM) but not under normal Pi condition (1 mM). The phoBR complementation strain HAL1-▵phoB-C reversed the mutants' phenotypes back to wild type status. Meanwhile, lacZ reporter fusions using pCM-lacZ showed that the expression of phoBR and aioBA were both induced by As(III) but were not induced in HAL1-phoR 931 and HAL1-▵phoB. Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region. PhoB was able to bind to the putative Pho box in vivo (bacterial one-hybrid detection) and in vitro (electrophoretic mobility gel shift assay), and an 18-bp binding sequence containing nine conserved bases were determined. This study provided the evidence that PhoBR regulates the expression of aioBA in Halomonas sp. HAL1 under low Pi condition. The new regulation model further implies the close metabolic connection between As and Pi.

No MeSH data available.


Related in: MedlinePlus