Frequency distribution of host-range mutants among T2 phage infected bacteria.

Phage. A plaque type mutant phage, T2 r tu, was used as a test bacteriophage. Its latent period and burst size, when incubated with Escherichia coli strain B cells in nutrient broth at 37 C, were about 20 min and 50, respectively. Host bacteria. Escherichia coli strain B was used as host. To select for host-range mutants, strain B/2 which is resistant to T2 was used. Techniques. Standard methods in phage work described by Adams (1950) were adopted. For basic medium, nutrient broth (pH 7.2) was used. Incubations were carried out at 37 C throughout the experiments. The details of the other experimental procedures will be described later.