Mutations of phage P22 affecting phage DNA synthesis and lysogenization

Two temperature-sensitive mutants of phage P22, ts18.1 and ts12.1, are described which have recessive DNA-negative phenotypes. At high temperature they fail to synthesize phage DNA. In mixed infection with the two mutants or either mutant and wild-type phage, DNA synthesis and phage production are normal. In addition, under non-permissive conditions, these mutants fail to lysogenize and show dominant integration-negative phenotypes. They do not complement for lysogenization in mixed infection and each of these mutants interferes with lysogenization by wild type. At low temperature each mutant shows normal phage production and normal frequencies of lysogenization. These mutant lysogens are stable at high temperature. The data suggest the requirement for common functions for genome replication and prophage integration. The muta-tions are closely linked and map just to the right of the c region in map positions analogous to genes 0 and P of phage h. 1