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Active Transport of Iron in Bacillus megaterium: Role of Secondary Hydroxamic Acids

By W. B. Davis and B. R. Byers


Kinetics of radioactive iron transport were examined in three strains of Bacillus megaterium. In strain ATCC 19213, which secretes the ferric-chelating secondary hydroxamic acid schizokinen, 59Fe3+ uptake from 59FeCl3 or the ferric hydroxamate Desferal-59Fe3+ was rapid and reached saturation within 3 min. In strain SK11, which does not secrete schizokinen, transport from 59FeCl3 was markedly reduced; the two ferric hydroxamates Desferal-59Fe3+ or schizokinen-59Fe3+ increased both total 59Fe3+ uptake and the 59Fe3+ appearing in a cellular trichloroacetic acid-insoluble fraction, although 10 min was required to reach saturation. Certain characteristics of transport from both ferric hydroxamates and FeCl3 suggest that iron uptake was an active process. The growth-inhibitory effect of aluminum on strain SK11 was probably due to the formation of nonutilizable iron-aluminum complexes which blocked uptake from 59FeCl3. Desferal or schizokinen prevented this blockage. A strain (ARD-1) resistant to the ferric hydroxamate antibiotic A22765 was isolated from strain SK11. Strain ARD-1 failed to grow with Desferal-Fe3+ as an iron source, and it was unable to incorporate 59Fe3+ from this source. Growth and iron uptake in strain ARD-1 were similar to strain SK11 with schizokinen-Fe3+ or the iron salt as sources. It is suggested that the ferric hydroxamates, or the iron they chelate, may be transported by a special system which might be selective for certain ferric hydroxamates. Strain ARD-1 may be unable to recognize both the antibiotic A22765 and the structurally similar chelate Desferal-Fe3+, while retaining its capacity to utilize schizokinen-Fe3+

Topics: Physiology and Metabolism
Year: 1971
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Provided by: PubMed Central
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