1978 Volume 24 Issue 6 Pages 297-306
A multiple mutant of bacteriophage T4, which had been proved to contain cytosine-substituted DNA, was grown in a suppressor-containing or non-containing (sup°) strain of Escherichia coli B or K12, and the progeny phage obtained was grown on test strains carrying various restriction systems. As a result, the growth of this phage was found to be subject to the rK, rB, and rP1 restriction systems. Two T4 strains, named UNF-r1 and UNF-r+1, sensitive to the rK, rB, and rP1 restriction systems, were newly derived by the genetic cross and mutagenesis. The former had the unf-39 mutation instead of the alc-8 mutation, the latter had the rII+ region and the unf-39 mutation, besides the amE51 (gene 56; dCTPase), denA (endonuclease II), and denB (endonuclease IV) mutations. It was demonstrated that UNF-r+1 DNA possessed a SalI recognition site in the rII-denB region which was deleted in UNF-r1 DNA.