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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

The gene island of As(III) oxidation in Halomonas sp. HAL1 and As(III) oxidation analysis. (A) The gene island of As(III) oxidation. The transposon insertion site of phoR mutant is shown by vertical arrow. (B). As(III) oxidation phenotype of strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C. The strains were inoculated into MMNH4 medium containing 0.1 mM Pi, 0.8 M NaCl, and 1 mM As(III). After 7 d cultivation, the As(III) oxidation was monitored by qualitative KMnO4 biochemical analysis.
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Figure 1: The gene island of As(III) oxidation in Halomonas sp. HAL1 and As(III) oxidation analysis. (A) The gene island of As(III) oxidation. The transposon insertion site of phoR mutant is shown by vertical arrow. (B). As(III) oxidation phenotype of strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C. The strains were inoculated into MMNH4 medium containing 0.1 mM Pi, 0.8 M NaCl, and 1 mM As(III). After 7 d cultivation, the As(III) oxidation was monitored by qualitative KMnO4 biochemical analysis.

Mentions: The draft genome sequencing of Halomonas sp. HAL1 revealed that an arsenic gene island located in contig 97 contains the As(III) oxidase genes aioBA, the arsenic efflux genes arsB-mcp-arsC-arsH1-acr3-arsH2 and the phosphate-related genes pstSCAB (Figure 1A) (Lin et al., 2012). However, the three-component regulator genes aioXSR were absent in the entire genome (Lin et al., 2012; Li et al., 2013). Genomic analysis revealed that only one copy of phoBR genes locating in contig 26. The two genes encode two-component system proteins, which is mainly a response to phosphate stress (Lin et al., 2012; Li et al., 2013).


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)

The gene island of As(III) oxidation in Halomonas sp. HAL1 and As(III) oxidation analysis. (A) The gene island of As(III) oxidation. The transposon insertion site of phoR mutant is shown by vertical arrow. (B). As(III) oxidation phenotype of strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C. The strains were inoculated into MMNH4 medium containing 0.1 mM Pi, 0.8 M NaCl, and 1 mM As(III). After 7 d cultivation, the As(III) oxidation was monitored by qualitative KMnO4 biochemical analysis.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 1: The gene island of As(III) oxidation in Halomonas sp. HAL1 and As(III) oxidation analysis. (A) The gene island of As(III) oxidation. The transposon insertion site of phoR mutant is shown by vertical arrow. (B). As(III) oxidation phenotype of strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C. The strains were inoculated into MMNH4 medium containing 0.1 mM Pi, 0.8 M NaCl, and 1 mM As(III). After 7 d cultivation, the As(III) oxidation was monitored by qualitative KMnO4 biochemical analysis.
Mentions: The draft genome sequencing of Halomonas sp. HAL1 revealed that an arsenic gene island located in contig 97 contains the As(III) oxidase genes aioBA, the arsenic efflux genes arsB-mcp-arsC-arsH1-acr3-arsH2 and the phosphate-related genes pstSCAB (Figure 1A) (Lin et al., 2012). However, the three-component regulator genes aioXSR were absent in the entire genome (Lin et al., 2012; Li et al., 2013). Genomic analysis revealed that only one copy of phoBR genes locating in contig 26. The two genes encode two-component system proteins, which is mainly a response to phosphate stress (Lin et al., 2012; Li et al., 2013).

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