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1. Metabolic Responses to Arsenite Exposure Regulated through Histidine Kinases PhoR and AioS in Agrobacterium tumefaciens 5A

   https://doi.org/10.3390/microorganisms8091339  

   Rawle, Rachel A. ; Tokmina-Lukaszewska, Monika ; Shi, Zunji ; Kang, Yoon-Suk ; Tripet, Brian P. ; Dang, Fang ; Wang, Gejiao ; McDermott, Timothy R. ; Copie, Valerie ; Bothner, Brian ( September 2020 , Microorganisms)

   null (Ed.)

   Arsenite (AsIII) oxidation is a microbially-catalyzed transformation that directly impacts arsenic toxicity, bioaccumulation, and bioavailability in environmental systems. The genes for AsIII oxidation (aio) encode a periplasmic AsIII sensor AioX, transmembrane histidine kinase AioS, and cognate regulatory partner AioR, which control expression of the AsIII oxidase AioBA. The aio genes are under ultimate control of the phosphate stress response via histidine kinase PhoR. To better understand the cell-wide impacts exerted by these key histidine kinases, we employed 1H nuclear magnetic resonance (1H NMR) and liquid chromatography-coupled mass spectrometry (LC-MS) metabolomics to characterize the metabolic profiles of ΔphoR and ΔaioS mutants of Agrobacterium tumefaciens 5A during AsIII oxidation. The data reveals a smaller group of metabolites impacted by the ΔaioS mutation, including hypoxanthine and various maltose derivatives, while a larger impact is observed for the ΔphoR mutation, influencing betaine, glutamate, and different sugars. The metabolomics data were integrated with previously published transcriptomics analyses to detail pathways perturbed during AsIII oxidation and those modulated by PhoR and/or AioS. The results highlight considerable disruptions in central carbon metabolism in the ΔphoR mutant. These data provide a detailed map of the metabolic impacts of AsIII, PhoR, and/or AioS, and inform current paradigms concerning arsenic–microbe interactions and nutrient cycling in contaminated environments. 

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2. Involvement of the Acr3 and DctA anti-porters in arsenite oxidation in A grobacterium tumefaciens 5A: Antiporter involvement in arsenite oxidation

   https://doi.org/10.1111/1462-2920.12468  

   Kang, Yoon-Suk ; Shi, Zunji ; Bothner, Brian ; Wang, Gejiao ; McDermott, Timothy R. ( June 2015 , Environmental Microbiology)
3. Fate of arsenate following arsenite oxidation in A grobacterium tumefaciens  GW4: As III oxidation and As V metabolism

   https://doi.org/10.1111/1462-2920.12465  

   Wang, Qian ; Qin, Dong ; Zhang, Shengzhe ; Wang, Lu ; Li, Jingxin ; Rensing, Christopher ; McDermott, Timothy R. ; Wang, Gejiao ( June 2015 , Environmental Microbiology)
4. Transcriptomics analysis defines global cellular response of Agrobacterium tumefaciens 5A to arsenite exposure regulated through the histidine kinases PhoR and AioS

   https://doi.org/10.1111/1462-2920.14577  

   Rawle, Rachel A. ; Kang, Yoon‐Suk ; Bothner, Brian ; Wang, Gejiao ; McDermott, Timothy R. ( April 2019 , Environmental Microbiology)

   In environments where arsenic and microbes coexist, microbes are the principal drivers of arsenic speciation, which directly affects bioavailability, toxicity and bioaccumulation. Speciation reactions influence arsenic behaviour in environmental systems, directly affecting human and agricultural exposures. Arsenite oxidation decreases arsenic toxicity and mobility in the environment, and therefore understanding its regulation and overall influence on cellular metabolism is of significant interest. The arsenite oxidase (AioBA) is regulated by a three‐component signal transduction system AioXSR, which is in turn regulated by the phosphate stress response, with PhoR acting as the master regulator. Using RNA‐sequencing, we characterized the global effects of arsenite on gene expression inAgrobacterium tumefaciens5A. To further elucidate regulatory controls, mutant strains for histidine kinases PhoR and AioS were employed, and illustrate that in addition to arsenic metabolism, a host of other functional responses are regulated in parallel. Impacted functions include arsenic and phosphate metabolism, carbohydrate metabolism, solute transport systems and iron metabolism, in addition to others. These findings contribute significantly to the current understanding of the metabolic impact and genetic circuitry involved during arsenite exposure in bacteria. This informs how arsenic contamination will impact microbial activities involving several biogeochemical cycles in nature.

    

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5. Arsenite oxidation regulator AioR regulates bacterial chemotaxis towards arsenite in Agrobacterium tumefaciens GW4

   Article | OPEN | Published: 03 March 2017 Shi, K ; Fan, X ; Qiao, Z ; Han, Y ; McDermott, TR ; Wang, Q ; Wang, G. ( March 2017 , Scientific reports)

   Some arsenite [As(III)]-oxidizing bacteria exhibit positive chemotaxis towards As(III), however, the related As(III) chemoreceptor and regulatory mechanism remain unknown. The As(III)-oxidizing bacterium Agrobacterium tumefaciens GW4 displays positive chemotaxis towards 0.5–2 mM As(III). Genomic analyses revealed a putative chemoreceptor-encoding gene, mcp, located in the arsenic gene island and having a predicted promoter binding site for the As(III) oxidation regulator AioR. Expression of mcp and other chemotaxis related genes (cheA, cheY2 and fliG) was inducible by As(III), but not in the aioR mutant. Using capillary assays and intrinsic tryptophan fluorescence spectra analysis, Mcp was confirmed to be responsible for chemotaxis towards As(III) and to bind As(III) (but not As(V) nor phosphate) as part of the sensing mechanism. A bacterial one-hybrid system technique and electrophoretic mobility shift assays showed that AioR interacts with the mcp regulatory region in vivo and in vitro, and the precise AioR binding site was confirmed using DNase I foot-printing. Taken together, these results indicate that this Mcp is responsible for the chemotactic response towards As(III) and is regulated by AioR. Additionally, disrupting the mcp gene affected bacterial As(III) oxidation and growth, inferring that Mcp may exert some sort of functional connection between As(III) oxidation and As(III) chemotaxis. 

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