title: Effects of Mg2+ and Ca2+ on Fe2+ uptake by Bifidobacterium thermophilum.
abstract: Ferrous iron uptake was investigated in Bifidobacterium thermophilum (B. thermophilum) in the presence of Mg2+ and Ca2+ with the following findings: 1. Mg2+ inhibited Fe2+ accumulation in the cells in a dose-dependent manner at 37 degrees, but not at 0 degrees. Removal of Mg2+ from the medium resulted in a resumption of rapid iron uptake. 2. Mg2+ had no effect on the binding of Fe2+ by B. thermophilum protoplasts, its cellular particulate fraction, or distribution between the particulate and soluble fractions. 3. Ca2+ exerted a stimulatory effect on iron uptake by B. thermophilum, but was not able to reverse the inhibitory effects of Mg2+. 4. It was concluded that Mg2+ has no effect on the binding of iron on the surface or interior of B. thermophilum and that it affected the Fe2+ transport mechanism (permease) in a reversible manner. It is possible that iron and magnesium share the same permease in this microorganism.
authors.affiliation: Department of Biochemistry, Rush-Presbyterian-St. Luke's Medical Center, Chicago, IL 60612.
authors.forename: E
authors.initials: E
authors.lastname: Kot
authors.forename: A
authors.initials: A
authors.lastname: Bezkorovainy
mesh_terms: D001644:Bifidobacterium / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology*; D007501:Iron / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology*; D011523:Protoplasts / Q000378:metabolism
chemical_list: D007501:Iron; D008274:Magnesium; D002118:Calcium