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Iron-uptake systems and transport in staphylococcus aureus / Ahmed Bensoltane 

Public ISBD Titre : Iron-uptake systems and transport in staphylococcus aureus Type de document : texte imprimé Auteurs : Ahmed Bensoltane, Auteur Editeur : Glasgow : University of Glasgow Année de publication : 1992 Importance : 143 f. Présentation : ill. Format : 27 cm. Note générale : Thèse de Doctorat : Microbiologie : Royaume-Uni, University of Glasgow : 1992 Bibliogr. f. 144 - 171 Annexe f. 172 - 179 Langues : Anglais (eng) Mots-clés : Iron-uptake  systems Staphylococci  isolated S.  aureus  strains Iron-chelators Thin  layer  chromatography Staphylococcus  aureus Index. décimale : D001392 Résumé : The main objective of this thesis was the characterisation of iron-uptake systems in staphylococci isolated from different sources and investigation of the possible role of these in pathogensis. The iron-uptake systems of S. aureus strains were investigated by growing the cells in the presence of different iron-chelators. With the synthetic iron-chelators, α,α-dipyridyl and EDDA, siderophores were produced which could not be detected by the Arnow assay for phenolates or the Csaky test for hydroxamates. They were detected by paper chromatography, by thin layer chromatography (TLC) and with the Chrome Azurol S (CAS, blue agar) plates of Schwyn and Neilands. The siderophore of S. aureus C336 was partially purified by solvent extraction, column chromatography and TLC and partially characterised as a phenolate. In the presence of the natural chelator, transferrin, staphylococci grew well but produced no detectable siderophore. As the rate of uptake of ⁵⁵Fe by staphylicocci was faster in the presence of transferrin than EDDA it appeared that staphylococci interacted directly with transferrin to obtain iron. Transferrin was radiolabelled with ¹²⁵-I and in competitive binding exoeriments to cells was indistinguishable from native transferrin. Radiolabelled transferrin bound rapidly to staphylococci, reaching saturation after approximately 20 minutes when approximately 350 and 206 molecules per cell were bound by S. aureus strains C336 and GRI-15586 respectively. The binding affinity of transferrin for staphylococci was low (8 x 10⁶ litres/mole) and cells were estimated to possess approximately 20000 binding sires for transferrin. In contrast to the pathogenic isolates of staphylococci, commensal strains of S. aureus from humans grew in the presence of EDDA but no siderophores were detectable with the CAS blue agar plates or the Arnow or Csaky assays. Addition of KCN to growing cultures of the commensals did not inhibit their growth, in contrast to the pathogenic isolates. It is concluded that staphylococci exhibit at least 3 responses to iron-restriction. They may interact directly with transferrin, produce siderophores or, in the case of commensals, grow without utilisation of iron. Pathogenic staphylococci may use the siderophore-mediated uptake system to provide iron in locations where transferrin is absent or present only in low concentration. Iron-uptake systems and transport in staphylococcus aureus [texte imprimé] / Ahmed Bensoltane, Auteur . - Glasgow : University of Glasgow, 1992 . - 143 f. : ill. ; 27 cm. Thèse de Doctorat : Microbiologie : Royaume-Uni, University of Glasgow : 1992 Bibliogr. f. 144 - 171 Annexe f. 172 - 179 Langues : Anglais (eng) Mots-clés : Iron-uptake  systems Staphylococci  isolated S.  aureus  strains Iron-chelators Thin  layer  chromatography Staphylococcus  aureus Index. décimale : D001392 Résumé : The main objective of this thesis was the characterisation of iron-uptake systems in staphylococci isolated from different sources and investigation of the possible role of these in pathogensis. The iron-uptake systems of S. aureus strains were investigated by growing the cells in the presence of different iron-chelators. With the synthetic iron-chelators, α,α-dipyridyl and EDDA, siderophores were produced which could not be detected by the Arnow assay for phenolates or the Csaky test for hydroxamates. They were detected by paper chromatography, by thin layer chromatography (TLC) and with the Chrome Azurol S (CAS, blue agar) plates of Schwyn and Neilands. The siderophore of S. aureus C336 was partially purified by solvent extraction, column chromatography and TLC and partially characterised as a phenolate. In the presence of the natural chelator, transferrin, staphylococci grew well but produced no detectable siderophore. As the rate of uptake of ⁵⁵Fe by staphylicocci was faster in the presence of transferrin than EDDA it appeared that staphylococci interacted directly with transferrin to obtain iron. Transferrin was radiolabelled with ¹²⁵-I and in competitive binding exoeriments to cells was indistinguishable from native transferrin. Radiolabelled transferrin bound rapidly to staphylococci, reaching saturation after approximately 20 minutes when approximately 350 and 206 molecules per cell were bound by S. aureus strains C336 and GRI-15586 respectively. The binding affinity of transferrin for staphylococci was low (8 x 10⁶ litres/mole) and cells were estimated to possess approximately 20000 binding sires for transferrin. In contrast to the pathogenic isolates of staphylococci, commensal strains of S. aureus from humans grew in the presence of EDDA but no siderophores were detectable with the CAS blue agar plates or the Arnow or Csaky assays. Addition of KCN to growing cultures of the commensals did not inhibit their growth, in contrast to the pathogenic isolates. It is concluded that staphylococci exhibit at least 3 responses to iron-restriction. They may interact directly with transferrin, produce siderophores or, in the case of commensals, grow without utilisation of iron. Pathogenic staphylococci may use the siderophore-mediated uptake system to provide iron in locations where transferrin is absent or present only in low concentration.

Exemplaires

Code-barres	Cote	Support	Localisation	Section	Disponibilité	Spécialité	Etat_Exemplaire
D001392	D001392	Papier	Bibliothèque centrale	Thèse de Doctorat	Disponible

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