Isolation and characterization of viable deletion mutants of Bacillus subtilis bacteriophage SPO2.

Spontaneous deletion mutants of the bacteriophage SPO2, which are viable and retain their temperate character, were isolated using a heat-EDTA enrichment step. They were identified by endonuclease digestion and agarose-gel electrophoresis of phage DNA. Two of the nine mutants were characterized in detail. Both mutants have a 2.3 Md deletion removing the single BglII site and two of the XbaI fragments. The deletion extends 1.0 Md to one side of the former BglII site and 1.3 Md on the other side. This region of the SPO2 genome is non-essential for either lysogeny or viable phage production and thus is a suitable region for the insertion of exogenous DNA fragments.