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The effects of the bactericidal protein colicin K have been compared on a normal strain of Escherichia coliand a derivative, uncA, that is defective in Ca2+, Mg2+-activated ATPase activity. The syntheses of DNA, RNA, and proteins, which are completely arrested by colicin K in the normal E. colicells, are only reduced by 30 to 50% in the ATPase-deficient cells. Intracellular ATP levels, which are reduced in the normal cells, are substantially increased by colicin K in the uncA mutant. The active transport of glutamine, which is coupled to phosphate bond energy, is drastically inhibited in both strains as is the transport of proline, a transport system that is coupled to an energized membrane state. These results provide the basis for the proposal that the primary action of colicin K is to de-energize the cytoplasmic membrane systems that are essential for a variety of active transport processes in E. coli. In cells having ATPase activity, ATP levels are diminished by the action of ATPase attempting to re-energize the membrane. This reduction in ATP levels in turn leads to an arrest of macromolecular biosyntheses. These secondary effects of colicin K on ATP levels and on synthetic processes are not present in uncA cells because they lack ATPase activity.

Presents a response by Salvador E. Luria to a letter to the editor about his article on teaching introductory biology in the March 1969 issue.

Focuses on physicist Edward Teller's views on proper course for Americans to follow in their efforts to cope with the problem of survival in a nuclear age in the U.S. Elaboration of the recipe for survival by Teller; Questions on the position of Teller in negotiated steps towards disarmament; Examination of the program for limited wars with a civil-defense system to protect people across the nation.