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 mug 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.