INHIBITORY ACTION OF PHAGE K ON STAPHYLOCOCCAL DEHYDROGENASES II

Abstract

Ralston , D. J. (University of California, Berkeley) and M. D. Perry . Inhibitory action of phage K on staphylococcal dehydrogenases. II. Its possible relationship to sensitization and cell lysis. J. Bacteriol. 86: 740–748. 1963.—By measuring the reduction of the dye triphenyl tetrazolium chloride to the insoluble red formazan, an analysis was made of the inhibition by phage K of the dehydrogenase capacity of populations of Staphylococcus aureus K 1 , to determine to what extent this might be associated with the ability of phage K to sensitize the cells—a reaction characterized by the conversion of the cell wall to susceptibility to lysis by the staphylococcal enzyme, virolysin. Increasing multiplicities of phage progressively increased the fractions of sensitized cells and also caused increasing inhibition of the dehydrogenase activity of the populations. The dehydrogenase activities of the sensitized fractions were compared with those of the nonsensitized fractions. Over a wide range of phage-bacterium ratios, the dehydrogenase activities of the sensitized fractions were found to be lower than those of the nonsensitized fractions. Microscopically, this was reflected by the appearance of large numbers of cells with a reduced amount of visible formazan granules. When lysin was added to the phage-treated cells, lysis occurred mainly from cell fractions which possessed little or no tetrazolium-reducing capacity. The data indicated that sensitization by phage was accompanied by a marked decrease in cellular dehydrogenase activity but was not associated with a complete inhibition of these enzymes. A comparison was made between the dehydrogenases of phage-sensitized cells and cells found to be “spontaneously” sensitive to virolysin, i.e., lysed by the enzyme without any prior exposure to phage. Like phage-sensitized cells, the spontaneously sensitized staphylococci possessed low dehydrogenase activity and lacked the capacity to support phage synthesis. In tests of a given cell preparation, the dehydrogenase levels of the phage-sensitized fractions were found to be close to, or even lower than, the level of the spontaneously sensitized fraction, suggesting that in S. aureus K 1 the sensitized state is associated in some manner with a reduction of the dehydrogenase activity to a critical level. There is as yet no evidence for any direct causal relationship between sensitization and dehydrogenase inhibition.