Genetic analysis of non-essential bacteriophage T7 genes

Isolation and genetic characterization of a series of deletions and point mutants affecting two non-essential genes of bacteriophage T7 is described. The T7 ligase gene falls between genes 1 and 2, and is designated gene 1.3. Another non-essential gene, designated gene 0.7, has been mapped to the left of gene 1. In order to facilitate isolation and characterization of these mutants, host strains were found in which one or both of these T7 genes is required for growth.