Symmetrical Patterns of Bacteriophage Production

Abstract

In a previous note 1 it was shown that the problem of how bacteriophages are produced can be directly approached through the electron microscopy of metal shadowed “replicas” of the surfaces of agar cultures on which bacteria and bacteriophage are growing together. Such studies of several different bacteriophages are showing many of the phenomena involved in the production of these virus-like objects. The processes are complex and depend not only on the type of bacterium and the strain of bacteriophage but also on such factors as the rate and the duration of growth of the culture. Detailed evidence furnished by the electron microscope will be described elsewhere.

One of the most impressive aspects of the development of bacteriophage from bacterial protoplasm is its completeness, and in certain instances its regularities. With the T3 bacteriophage against the colon bacillus, the pattern of this conversion shows a symmetry as perfect as that of the molecular particles in a crystalline array 2 (Fig. 1). As in this figure the pattern often covers the entire surface of a bacterium; but it is also to be seen spreading throughout extruded protoplasm (Fig. 2). It extends into and includes the thick masses which were bipolar bodies in the original cells. When most clearly visible, the pattern is one of concavities but in many places the separate indentations are filled with spherical bodies having the size of free bacteriophage particles. Photographs have been obtained of this honeycomb structure starting to form within cells that otherwise seem normal; but it is often difficult to be sure whether these indentations are places where fully formed particles have escaped or where relatively immature particles are just beginning to form.

Correspondingly complete conversion to bacteriophage has been observed with other strains but highly symmetrical nets of particles have not been seen following infection with any of the “tailed” bacteriophages.