Isolation of viable deletion mutants of Streptomyces actinophage (Pal 6) and their molecular characterization.

Deletion mutants of bacteriophage Pal 6 were isolated by successive treatments of either heat (60 degrees C) or pyrophosphate (10 mM). These mutants were characterized by restriction enzyme cleavage analysis. The pyrophosphate resistant clones lost the whole Eco R1 fragment in which the Sal I site is located, as well as an unrelated Hind III fragment. These results show that the region containing the Sal I site in the phage genome is not essential for phage viability. This single Sal I site is therefore suitable as a potential insertion site for DNA cloning. On the other hand, the heat resistant clones that were isolated and characterized do not appear to have detectable deletions as indicated by their Eco R1 DNA digestion pattern.