Deletion mutants of temperate Bacillus subtilis bacteriophage phi105

Six deletion mutants of temperate Bacillus subtilis phage phi105 have been isolated on the basis of their increased resistance to chelating agents. The size and position of the deletions was determined by electronmicroscopy of DNA heteroduplexes. All deletions are located in a region about 55-70% from one end of the DNA molecule, in the right half of the known genetic map of the phage. The segment 55-65% does not contain any genes essential for lytic growth or lysogenization. A gene(s) for immunity is located in a segment 65-70% from the left end. By electronmicroscopy by partially denatured phi105 DNA two A-T rich regions have been localized in the right half of the molecule. One of these regions falls within the non-essential 55-65% DNA segment.