Multiple lysogeny from single infection

Abstract

Upon infection of either Shigella dysenteriae strain Sh or Escherichia coli strain C with temperate phage P2, some isolates possessing the high level of immunity typical of doubly lysogenic strains are recovered. They represent about 2% of all lysogenic clones, independently of the number of phage particles infecting the host cells. For E. coli C, bacterial crosses indicate the presence in these exceptional isolates of prophages at two chromosomal sites, one of which is, possibly as a rule, the preferred site for P2 (location I). In one case, the other site involved appears to be a previously recognized second-choice location.