title: Constitutive expression of the iron-enterochelin and ferrichrome uptake systems in a mutant strain of Salmonella typhimurium.
abstract: Two high-affinity iron uptake systems are known in Salmonella typhimurium, one utilizing iron-enterochelin and the other utilizing ferrichrome. It has been shown previously that expression of several elements of the iron-enterochelin uptake system are regulated by the iron content of the medium, with growth in high-iron medium resulting in repression of enzymes of enterochelin synthesis and degradation and of the ability of whole cells to take up iron-enterochelin. In this study we describe a mutant strain in which growth in high-iron medium was associated with constitutive expression of: (i) iron-enterochelin uptake by whole cells; (ii) ferrichrome uptake by whole cells; (iii) synthesis of enterochelin; (iv) intracellular degradation of iron-enterochelin; and (v) synthesis of three major outer membrane proteins (OM1, OM2, and OM3). In contrast, in the wild-type strain these properties were expressed only after growth in iron-deficient medium. It is proposed that the mutation affects a gene responsible for regulating expression of the structural genes for the components of the high-affinity iron uptake systems. The term fur, for iron (Fe) uptake regulation, is suggested for this new class of mutant.
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D001692:Biological Transport; D004758:Enterobactin / Q000378:metabolism*; D005291:Ferrichrome / Q000378:metabolism*; D005809:Genes, Regulator; D006877:Hydroxamic Acids / Q000378:metabolism*; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D008565:Membrane Proteins / Q000096:biosynthesis*; D009154:Mutation; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000031:analogs & derivatives*
chemical_list: D001426:Bacterial Proteins; D006877:Hydroxamic Acids; D008565:Membrane Proteins; D005291:Ferrichrome; D004758:Enterobactin; D012694:Serine; D007501:Iron