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

Abstract

The u.-v. 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 u.-v. light micrographs to be characteristic of penicillin-treated S. 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 Staphylococcus K phage to the surface of S. 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 S. aureus by the combined action of phage and penicillin was not associated with any peculiarity in micrographic appearance, except that with high concns. of penicillin the number of phage particles released on lysis was diminished. During air- and freeze-drying the diameter of S. 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 m[mu]/diam. and a slender tail 200-250 m[mu]long.