Uniformity of Size of Bacteriophage Particles

Abstract

The relative rates of centrifugal sedimentation, and of diffusion through agar, of bacteriophages T1 and T2K in mixtures, were measured by assaying the 2 types of phage in supernates and diffusates on selective bacterial strains. Tl was found to diffuse more rapidly, and to sediment more slowly, than T2K. Attempts to obtain a fraction of T2K of smaller size relative to Tl, by ultrafiltration or fractional centrifugation, failed completely. It is concluded that the minimal size of particles of T2K is not appreciably less than the average size of the unfraction-ated material, and is certainly greater than that of Tl. Several independent lines of evidence now show that the particles of T2K and certain related phages are nearly perfectly infectious.