A new gene of bacteriophage T4 determining immunity against superinfecting ghosts and phage in T4-infecfed Escherichia coli

Abstract

Bacteriophage T4 can form progeny in Escherichia coli cells infected with ghosts if the phage infection precedes that of the ghosts by a few minutes. In an accompanying article (Vallée et al., 1972) we report that a mutant of T4, amE142(39), is unique as compared to 21 other gene 39 mutants in that it fails to protect host cells against ghosts. S. Mufti (personal communication) has shown that this same mutant was not able to exclude superinfecting phage. Evidence is now presented that amE142(39) contains a second mutation probably located between genes 42 and 43 on the T4 genome. This second mutation, defining a new gene (imm) has been separated from the amber mutation of the parent strain amE142(39) and shown to be responsible for the failure to protect T4-infected cells against superinfecting T4 ghosts or phage. The failure to establish immunity appears to be the only demonstrable phenotype of the imm − mutant. The immunity function seems to be dispensable to the phage.