Observations on the bacteriophagy of Erwinia carotovora.

The lysis of Erwinia carotovora by bacteriophage has been reported by Coons and Kotila (1925), but the morphological characteristics of the virus could not be studied at that time, prior to the methods of electron microscopy, and some of the important physiological characteristics have not been investigated. In undertaking to obtain further data on these aspects of the problem, we have obtained, by usual procedures, a preparation of bacteriophage active against a strain of this organism2 that causes a soft rot of onions. Before studying the characteristics of the lytic agent, phage stocks were prepared by successive isolation of single plaques, as a routine procedure of purification. With the final preparation, however, electron micrographs of the material from each of a number of apparently single, well-isolated plaques revealed an extraordinary diversity of phage and phagelike particles, whereas a single type had been expected. Although the interpretation of this phenomenon is not yet clear, the essential facts, which are presented and briefly discussed in this report, are of interest and they invite further investigation. Observations on the morphology of the host cells, as revealed by the electron microscope, as well as data on the one-step growth of the virus (Delbruick and Luria, 1942) are also included.