Isolation of nonsense mutants of lipid-containing bacteriophage PRD1

We isolated nonsense mutants of bacteriophage PRD1, a lipid-containing polyhedral virus capable of infecting many genera of gram-negative bacteria. These mutants were grouped into 19 classes on the basis of genetic complementation and sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis. PRD1 infection led to the synthesis of at least 25 viral proteins, 17 of which were components of mature virions. The synthesis of proteins fell into the following three classes: very early, middle early, and late. Two of the very early proteins, P1 and P8, had an effect on DNA synthesis, host protein synthesis shutoff, and the turning on of middle and late protein synthesis. Another very early protein, P12, was involved in the shutoff of early protein synthesis. Two genes were identified as affecting lysis of the host. One appeared to be a lysin, whereas the other was an accessory lytic factor.