Diffusion Constants of the E. coli Bacteriophages

Abstract

For determining the diffusion constants of substances which can be obtained pure in relatively large amounts, the conventional optical method of Lamm is most suitable. Unstable substances like bacteriophages and animal viruses, however, are often irreversibly altered by the purification procedures, and diffusion measurements on such systems are then subject to large errors. The diffusion of such substances is better investigated using impure solutions that are quantitatively evaluated through measurements of their biological activities.

Hershey, Kimura and Bronfenbrenner 1 have estimated the relative sizes of T 1 and T 2 bacteriophages against E. coli by measuring their diffusion through thin agar, but such measurements are difficult to evaluate because of the different adsorption of these bacteriophages by the pores of the agar. The present paper is a preliminary account of the application of another diffusion technique to a tailed, T₄ and a tailless, T₃, bacteriophage. These bacteriophages were chosen to find out if the tail influences diffusion as well as to compare particle sizes computed from diffusion measurements with those measured with the electron microscope.

The method is essentially that previously employed by the author to determine the diffusion constant of African horse sickness virus. 2 , 3 The apparatus consists of 4 multi-chambered diffusion cells clamped onto a base plate provided with levelling screws. Sharp interfaces between bacteriophage and medium were formed by filling adjacent cells with medium and bacteriophage suspension and by rotating the top sections of the cells relative to the bottom until the 2 liquids came into exact apposition to one another. This was done by watching the index lines on the sides of the cells. The bacteriophage solution was diluted with 1% glucose broth solution to increase boundary stability and to insure a diffusion process free from disturbances by convection.