The effect of carriage of P2 prophage on infections with phages of the T5 group.

Coliphage T5 and its hybrids with Salmonella phage PB have been described by Adams (J. Immunol., 67, 313, 1951), and the cytological effects of these phages have been described by Murray and Whitfield (J. Bacteriol. 65, 715, 1953). The cytological effects of the two parental phages differed in the later stages of infection, and this characteristic appeared to segregate independently of the genetic markers used by Adams. During studies of lysogenic and nonlysogenic Shigella dysenteriae strain Sh (Bertani, J. Bacteriol., 62, 293, 1951; Ann. inst. Pasteur, 84, 273, 1953; Cold Spring Harbor Symposia Quant. Biol., 18, 65, 1953), further information on the properties of T5, PB, and their hybrids was obtained. The methods used in these studies have been described (Whitfield and Murray, Can. J. Microbiol., 1, 216, 1954). S. dysentriae, Escherichia coli strain B, E. coli strain C, and the derived strains carrying the potential to produce either phage P1 or phage P2 (denoted by Sh(Pl), Sh(P2), etc.) were obtained from Dr. G. Bertani. The hybrids of T5 and PB phages were supplied by Dr. M. H. Adams. The ability to form plaques on a given host cell indicated multiplication on that host; up to 107 active phages were plated in each test. Adsorption of phage onto host cells was determined and was checked cytologically by the appearance of the first stage of infection; every phage adsorbed onto the host cells used. The results are expressed in table 1; other phages of the group (BG3, 29a, and PB1) behaved similarly to T5. Cytologically, the first stage of infection appeared normally in Sh(P2), but none of the stages indicative of phage mul-