title: Quorum sensing regulates dpsA and the oxidative stress response in Burkholderia pseudomallei.
abstract: Burkholderia pseudomallei is the causative agent of melioidosis, a fatal human tropical disease. The non-specific DNA-binding protein DpsA plays a key role in protecting B. pseudomallei from oxidative stress mediated, for example, by organic hydroperoxides. The regulation of dpsA expression is poorly understood but one possibility is that it is regulated in a cell population density-dependent manner via N-acylhomoserine lactone (AHL)-dependent quorum sensing (QS) since a lux-box motif has been located within the dpsA promoter region. Using liquid chromatography and tandem mass spectrometry, it was first established that B. pseudomallei strain PP844 synthesizes AHLs. These were identified as N-octanoylhomoserine lactone (C8-HSL), N-(3-oxooctanoyl)homoserine lactone (3-oxo-C8-HSL), N-(3-hydroxyoctanoyl)-homoserine lactone (3-hydroxy-C8-HSL), N-decanoylhomoserine lactone (C10-HSL), N-(3-hydroxydecanoyl) homoserine lactone (3-hydroxy-C10-HSL) and N-(3-hydroxydodecanoyl)homoserine lactone (3-hydroxy-C12-HSL). Mutation of the genes encoding the LuxI homologue BpsI or the LuxR homologue BpsR resulted in the loss of C8-HSL and 3-oxo-C8-HSL synthesis, demonstrating that BpsI was responsible for directing the synthesis of these AHLs only and that bpsI expression and hence C8-HSL and 3-oxo-C8-HSL production depends on BpsR. In bpsI, bpsR and bpsIR mutants, dpsA expression was substantially down-regulated. Furthermore, dpsA expression in Escherichia coli required both BpsR and C8-HSL. bpsIR-deficient mutants exhibited hypersensitivity to the organic hydroperoxide tert-butyl hydroperoxide by displaying a reduction in cell viability which was restored by provision of exogenous C8-HSL (bpsI mutant only), by complementation with the bpsIR genes or by overexpression of dpsA. These data indicate that in B. pseudomallei, QS regulates the response to oxidative stress at least in part via the BpsR/C8-HSL-dependent regulation of DpsA.
authors.affiliation: Department of Pathology, Faculty of Medicine-Ramathibodi Hospital, Mahidol University, Rama VI Road, Bangkok 10400, Thailand.
authors.forename: Putthapoom
authors.initials: P
authors.lastname: Lumjiaktase
authors.affiliation: Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Diggle
authors.affiliation: Department Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok, 10210, Thailand.
authors.forename: Suvit
authors.initials: S
authors.lastname: Loprasert
authors.affiliation: Department of Biochemistry, Faculty of Sciences, Mahidol University, Rama VI Road, Bangkok 10400, Thailand.
authors.forename: Sumalee
authors.initials: S
authors.lastname: Tungpradabkul
authors.affiliation: Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Mavis
authors.initials: M
authors.lastname: Daykin
authors.affiliation: Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Miguel
authors.initials: M
authors.lastname: Cámara
authors.affiliation: Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Williams
authors.affiliation: Department of Pathology, Faculty of Medicine-Ramathibodi Hospital, Mahidol University, Rama VI Road, Bangkok 10400, Thailand.
authors.forename: Mongkol
authors.initials: M
authors.lastname: Kunakorn
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000096:biosynthesis; D000222:Adaptation, Physiological; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000096:biosynthesis; D016957:Burkholderia pseudomallei / Q000235:genetics / Q000502:physiology*; D002853:Chromatography, Liquid; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D050296:Microbial Viability; D018384:Oxidative Stress; D053038:Quorum Sensing / Q000502:physiology*; D053719:Tandem Mass Spectrometry; D001616:beta-Galactosidase / Q000096:biosynthesis; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C088386:homoserine lactone; D020122:tert-Butylhydroperoxide; D001616:beta-Galactosidase; D015107:4-Butyrolactone