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  • 1
    Electronic Resource
    Electronic Resource
    Uptake of iron byGeotrichum candidum, a non-siderophore producer (1988)
    Springer
    BioMetals 1 (1988), S. 99-105 
    Details
    ISSN: 1572-8773
    Keywords: Iron ; Ferrioxamine B ; Transport ; Geotrichum candidum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Geotrichum candidum (isolate 1–9) pathogenic on citrus fruits, appears to lack siderophore production. Iron uptake byG. candidum is mediated by two distinct iron-regulated, energy-and temperature-dependent transport systems that require sulfhydryl groups. One system exhibits specificity for either ferric or ferrous iron, whereas the other exhibits specificity for ferrioxamine-B-mediated iron uptake and presumably other hydroxamate siderophores. Radioactive iron uptake from59FeCl3 showed an optimum at pH 6 and 35° C, and Michaelis-Menten kinetics (apparentK m = 3 μm,V max = 0.054 nmol · mg−1 · min−1). The maximal rate of Fe2+ uptake was higher than Fe3+ (V max = 0.25 nmol · mg−1 · min−1) but theK m was identical. Reduction of ferric to ferrous iron prior to transport could not be detected. The ferrioxamine B system exhibits an optimum at pH 6 and 40° C and saturation kinetics (K m = 2 μM,V max = 0.22 nmol · mg−1 · min−1). The two systems were distinguished as two separate entities by negative reciprocal competition, and on the basis of differential response to temperature and phenazine methosulfate. Mössbauer studies revealed that cells fed with either57FeCl3 or57FeCl2 accumulated unknown ferric and ferrous binding metabolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01138067
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of siderophores produced by different species of the dermatophytic fungiMicrosporum andTrichophyton (1992)
    Springer
    BioMetals 5 (1992), S. 213-216 
    Details
    ISSN: 1572-8773
    Keywords: Microsporum ; diderophores ; Trichophyton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The dermatophytic fungiTrichophyton spp andMicrosporum spp secrete ferrichrome type siderophores under low iron conditions. Three different species ofMicrosporum, i.e.M. qypseum, M. canis andM. audouinii, as well asT. rubrum produce ferrichrome C and ferricrocin, whereasT. mentagrophytes andT. tonsurans produce only ferrichrome. The identification of the siderophores was established by means of thin layer chromatography, high performance liquid chromatography and mass spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061220
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of siderophore-mediated iron transport inGeotrichum candidum, a non-siderophore producer (1990)
    Springer
    BioMetals 2 (1990), S. 209-213 
    Details
    ISSN: 1572-8773
    Keywords: Iron ; Siderophores ; Transport ; Geotrichum candidum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Geotrichum candidum is capable of utilizing iron from hydroxamate siderophores of different structural classes. The relative rates of iron transport for ferrichrome, ferrichrysin, ferrioxamine B, fusigen, ferrichrome A, rhodotorulic acid, coprogen B, dimerium acid and ferrirhodin were 100%, 98%, 74%, 59%, 49%, 35%, 24%, 12% and 11% respectively. Ferrichrome, ferrichrysine and ferrichrome A inhibited [59Fe]ferrioxamine-B-mediated iron transport by 71%, 68% and 28% respectively when added at equimolar concentrations to the radioactive complex. The inhibitory mechanism of [59Fe]ferrioxamine B uptake by ferrichrome was non-competitive (K i 2.4 μM), suggesting that the two siderophores do not share a common transport system. Uptake of [59Fe]ferrichrome, [59Fe]rhodotorulic acid and [59Fe]fusigen was unaffected by competition with the other two siderophores or with ferrioxamine B. Thus,G. candidum may possess independent transport systems for siderophores of different structural classes. The uptake rates of [14C]ferrioxamine B and67Ga-desferrioxamine B were 30% and 60% respectively, as compared to [59Fe]ferrioxamine B. The specific ferrous chelates, dipyridyl and ferrozine at 6 mM, caused 65% and 35% inhibition of [59Fe]ferrioxamine uptake. From these results we conclude that, although about 70% of the iron is apparently removed from the complex by reduction prior to being transported across the cellular membrane, a significant portion of the chelated ligand may enter the cell intact. The former and latter mechanisms seem not to be mutually exclusive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01141361
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