NONPERMISSIVENESS OF STRAIN B FORESCHERICHIA COLITO P1kc; THE ISOLATION OF P1bc

Abstract

P1kc grown on strain K12 of Escherichia coli adsorbs to, kills, lysogenizes and transduces strain B, but its efficiency of plating (e.o.p.) in strain B is 10⁻⁶. From the few plaques which form a mutant, P1bc, was derived which grows normally on strain B and has an e.o.p. of 5 × 10⁻³on K12. P1bc grown on K12 has an e.o.p. of 5 × 10⁻³on B. This reciprocal restriction is probably attributable to restriction and modification (r and m). P1kc has an e.o.p. of 5 × 10⁻³on strain B/r. Phage harvested from this infection have an e.o.p of 10⁻⁵on strain B and 5 × 10⁻³on K12. P1kc is restricted on strain B/r only to the extent determined by r and m, and P1bc is not selected under these conditions.