Genetic evidence for restriction targets in the DNA of phages λ and φ 80

Abstract
Temperate phages φ 80 and λ grown inE. colistrain C differ markedly in the degree to which they are restricted byE. colistrain K. The basis of this difference is subject to genetic recombination and deletion. The loss of restriction sensitivity by deletion shows that sensitivity is determined by loci in the phage genome. These loci are interpreted to be targets of the restriction mechanism, in agreement with previous biochemical evidence.