Working with Phage P22.

Transduction experiments in and are usually performed with virulent phage variants. A widely used P1 mutant, called P1 , carries one or more uncharacterized mutations that prevent formation of lysogens. In the case of P22, by far the most frequently used variant is named P22 HT105/1 This phage has a high transducing (HT) frequency due to a mutant nuclease with lower specificity for the sequence. As a result, ∼50% of the P22 HT phage heads carry random transducing fragments of chromosomal DNA. The mutation reduces the formation of stable lysogens. The basic steps in handling the P22 HT105/1 phage and in performing transduction experiments in are described here.