title: Role of the Irr protein in the regulation of iron metabolism in Rhodobacter sphaeroides.
abstract: In Rhizobia the Irr protein is an important regulator for iron-dependent gene expression. We studied the role of the Irr homolog RSP_3179 in the photosynthetic alpha-proteobacterium Rhodobacter sphaeroides. While Irr had little effect on growth under iron-limiting or non-limiting conditions its deletion resulted in increased resistance to hydrogen peroxide and singlet oxygen. This correlates with an elevated expression of katE for catalase in the Irr mutant compared to the wild type under non-stress conditions. Transcriptome studies revealed that Irr affects the expression of genes for iron metabolism, but also has some influence on genes involved in stress response, citric acid cycle, oxidative phosphorylation, transport, and photosynthesis. Most genes showed higher expression levels in the wild type than in the mutant under normal growth conditions indicating an activator function of Irr. Irr was however not required to activate genes of the iron metabolism in response to iron limitation, which showed even stronger induction in the absence of Irr. This was also true for genes mbfA and ccpA, which were verified as direct targets for Irr. Our results suggest that in R. sphaeroides Irr diminishes the strong induction of genes for iron metabolism under iron starvation.
authors.affiliation: Institut für Mikrobiologie und Molekularbiologie, University of Giessen, Giessen, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Peuser
authors.forename: Bernhard
authors.initials: B
authors.lastname: Remes
authors.forename: Gabriele
authors.initials: G
authors.lastname: Klug
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D005816:Genetic Complementation Test; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D000090463:Iron Deficiencies; D009154:Mutation / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D016366:Open Reading Frames / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015203:Reproducibility of Results; D012242:Rhodobacter sphaeroides / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D059467:Transcriptome / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D018076:DNA, Complementary; D017382:Reactive Oxygen Species; D014157:Transcription Factors; C114259:iron response regulator protein, Bacteria; D007501:Iron