Altered cotransduction frequencies exhibited by HT-mutants of Salmonella-phage P22.

Phage P22-mutants with increased transduction ability (HT-mutants) show in comparison to wild type 22, different frequencies of contransduction for markers on two different transducing fragments of the Salmonella chromosome. The data are interpreted as indicating that host DNA to be packaged is cut by HT-mutants at sites different from those cut by wild-type phage, due to an altered specificity of the nuclease responsible for this step.