The Influence of Antibacterial Substances on the Interaction of Bacteria and Bacteriophages: 2. Optical Studies of the Penicillin Effect

SUMMARY: The ultra-violet light and electron microscopes were used to observe the effect of bacteriophage and penicillin on Staphylococcus aureus. Penicillin caused the organisms to swell to almost twice their normal size, and immediately before lysis they became less opaque to electrons and internal structure was evident. The triply segmented cocci seen in the ultra-violet light micrographs to be characteristic of penicillin-treated Staph. aureus appear to be due to the irregular arrest of the process of division, whereby a cell partly divides and then only one of the incipient daughter cells partly divides again. The adsorption of the Staph. K phage to the surface of Staph. aureus, the latent period during which the coccus enlarges and the phage multiplies, and the lysis of the cell with liberation of phage particles were also recorded optically. Accelerated lysis of Staph. aureus by the combined action of phage and penicillin was not associated with any peculiarity in micrographic appearance, except that with high concentrations of penicillin the number of phage particles released on lysis was diminished. During air- and freeze-drying the diameter of Staph. aureus contracts by 30--50%. Electron micrographs of Staph. K bacteriophage, gold-shadowed and unshadowed, show a round head totally opaque to 50 kV. electrons, 50--60 mμ. in diameter, and a slender tail 200-250 mμ. in length.