Ultraviolet Irradiation of Bacteriophage During Intracellular Growth

Abstract

Cells of Escherichia coli infected with phage were irradiated with u.-v. light (2537A) at various times between infection and phage liberation, and the survival curves for ability to liberate phage were analyzed. Suppression of this ability resulted from inactivation of intra-cellular phage particles. In the course of the intracellular phage growth there is first an increase in u.-v. resistance of the individual particles, followed by multiplication. Part of the early increase in u.-v. resistance appears to depend on the presence of some component of the phage lysates other than active phage itself. The survival curves for bacteria infected with >1 particle of a phage strain (multiple infection) show that suppression of phage liberation requires a number of "hits" (primary photochemical reactions) similar to the number of infecting particles, suggesting that several particles of the same phage can grow in the same bacterial cell. The results are discussed in relation to the possible mechanisms of bacteriophage growth.