Effect of Various Metals and Calcium Metabolism Inhibitors on the Growth of Bifidobacterium bifidum Var. pennsylvanicus

Summary In view of the facts that the normal intestinal flora exerts beneficial effects and that bifidobacteria are a more important component in the breast‐fed than in the bottle‐fed infant, factors affecting the growth of the latter microorganisms are of interest. A series of transition and other metals were shown to be growth inhibitors of Bifidobacterium bifidum var. pennsylvanicus. Such inhibition could be reversed fully or partially by 0.5–1.0 mM Fe2+ in the case of Zn2+, Cu2+, Au3+, Pt4+, La3+, Cr3+ Mn2+, Ni2+, and Cd2+, but not with Ag+, Hg2+, and VO2+. In addition, 2–4 mM Ca2+ substantially relieved the inhibitory effects of Zn2+, Mn2+, and La3+, and partially relieved the effects of Cd2+. Mg2+ was ineffective in relieving Zn2+ inhibition, but Ba2+ and Sr2+ could replace Ca2+ to some extent. The calcium metabolism antagonists verapamil, ruthenium red, 2‐chloroadenosine, lasalocid, Ca‐ionophore A‐23187, and calmodulin inhibitors W‐5 and W‐7 inhibited microbial growth. Inhibition could be relieved fully or partially with 0.5–1 mM Fe2+. Mg2+ relieved the inhibition by lasalocid, Ca‐ionophore A‐23187, and verapamil, whereas Ca2+ was effective only in the case of Ca‐ionophore A‐23187. We conclude that calcium and magnesium fluxes play an important role in the physiology of the bifidobacteria and that several metal growth inhibitors interfere with iron metabolism.