Effects of the Rare Earth Cerium on Escherichia coli

The rare earth cerium was found to bind rapidly to Escherichia coli . Cerium inhibited oxygen uptake in the presence of glucose as well as the endogenous respiration of glucose-grown cells. For a cell concentration of 4 mg per ml, maximal inhibition was obtained at 120 μg per ml. Greater concentrations did not increase the inhibitory effect. Cerium inhibited 14 CO 2 evolution and 14 C uptake from uniformly labeled glucose. Marked changes in the distribution of 14 C incorporated into different chemical fractions of the cell were noted. The most striking changes occurred in the alcohol- and alcohol ether-soluble fractions, in which the 14 C activity was increased 5- to 20-fold in the presence of cerium.