A cytological study of the lysogenization of Shigella dysenteriae with P1 and P2 bacteriophages.

Abstract

Cytological studies have clarified the changes within the cell during the process of lysogenization by dysentery phages P1 and P2. The first stage of infection with both phages consisted of a condensation of the nuclear chromatin into annular bodies and axial filaments; there were differences in the later stages. With P1 infections, the annular and filament stages occupied about one half the latent period. The following phase consisted of expansion of the chromatinic aggregates into complex chromatinic reticula which, in the case of lysogenization, separated into discrete normal nuclear elements. The resulting cells were indistinguishable from those of the sensitive strain. In P1 virulent infections, the same stages were observed, but the cells lysed while in the expansion phase. In P2 infections, the chromatin aggregated into axial filaments, but the filaments persisted throughout the entire latent period and persisted up to lysis in the virulent infections. During lysogenization, the filament separated into discrete normal nuclear elements. The expansion was usually more advanced at the poles of the elongate cells; the first normal cells arose from this region. There is a considerable condensation of chromatin in the infected cell but the structure of the aggregates and the mode of recovery suggest that the fundamental organization of the constituents of the nuclear organelle must be retained.