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Updated: Aug 3, 2026

Essential Metal Uptake in Gram-negative Bacteria: X-ray Fluorescence, Radioisotopes, and Cell Fractionation
Published on: February 1, 2018
Ferrous iron uptake by Bifidobacterium breve
1Department of Biochemistry, Rush Presbyterian-St. Luke's Medical Center, Chicago, IL 60612.
Abstract:
Bifidobacterium breve transports ferrous iron in preference to the ferric form in a saturable, concentration-dependent manner with an optimum pH of 6. Iron transport is highly temperature sensitive. Two transport systems with apparent Km's of 86 +/- 27 and 35 +/- 20 microM (p greater than 0.01) were distinguished, one operating at high iron concentrations, the other at low iron concentrations. Iron uptake could not be accounted for by surface binding. Uptake of iron was inhibited by iron chelators, a protein ionophore, and ATPase inhibitors, and it was stimulated by potassium ionophores. The presence of a ferri reductase in the insoluble cell fraction of B. breve and its "spent" growth medium was demonstrated. The hypothesis is presented that iron uptake by bifidobacteria is related to the nutritional immunity phenomenon.
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