title: The ActP acetate transporter acts prior to the PitA phosphate carrier in tellurite uptake by Escherichia coli.
abstract: The tellurium oxyanion tellurite is harmful for most microorganisms. Since its toxicity occurs chiefly once the toxicant reaches the intracellular compartment, unveiling the toxicant uptake process is crucial for understanding the whole phenomenon of tellurium toxicity. While the PitA phosphate transporter is thought to be one of the main paths responsible for toxicant entry into Escherichia coli, genetic and physiological evidence have identified the ActP acetate carrier as the main tellurite importer in Rhodobacter capsulatus. In this work, new background on the role of these transporters in tellurite uptake by E. coli is presented. It was found that, similar to what occurs in R. capsulatus, ActP is able to mediate toxicant entry to this bacterium. Lower reactive oxygen species levels were observed in E. coli lacking the actP gene. Antioxidant enzyme catalase and fumarase C activity was almost unchanged after short exposure of E. coli ΔactP to sublethal tellurite concentrations, suggesting a low antioxidant response. In this strain, tellurite uptake decreased significantly during the first 5 min of exposure and inductively coupled plasma optical emission spectroscopy assays using an actP-overexpressing strain confirmed that this carrier mediates toxicant uptake. Relative gene expression experiments by qPCR showed that actP expression is enhanced at short times of tellurite exposure, while pitA and pitB genes are induced later. Summarizing, the results show that ActP is involved in tellurite entry to E. coli and that its participation occurs mainly at early stages of toxicant exposure.
authors.affiliation: Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile; Facultad de Ciencias de la Salud, Universidad San Sebastián, Santiago, Chile.
authors.forename: Alex
authors.initials: A
authors.lastname: Elías
authors.affiliation: Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile; Facultad de Ciencias de la Salud, Universidad San Sebastián, Santiago, Chile.
authors.forename: Waldo
authors.initials: W
authors.lastname: Díaz-Vásquez
authors.affiliation: Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: María José
authors.initials: MJ
authors.lastname: Abarca-Lagunas
authors.affiliation: Department of Chemistry and Texas Research Institute for Environmental Studies, Sam Houston State University, Huntsville, TX, USA.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Chasteen
authors.affiliation: Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Felipe
authors.initials: F
authors.lastname: Arenas
authors.affiliation: Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile. Electronic address: claudio.vasquez@usach.cl.
authors.forename: Claudio C
authors.initials: CC
authors.lastname: Vásquez
mesh_terms: D001692:Biological Transport; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D027501:Monocarboxylic Acid Transporters / Q000235:genetics / Q000378:metabolism*; D028061:Phosphate Transport Proteins / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D013691:Tellurium / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: C478943:ActP protein, E coli; D029968:Escherichia coli Proteins; D027501:Monocarboxylic Acid Transporters; D028061:Phosphate Transport Proteins; C534516:PitA protein, E coli; C026660:tellurous acid; D013691:Tellurium
keywords: ActP; Escherichia coli; Tellurite uptake