Physical mapping of bacteriophage P2 mutations and their relation to the genetic map.

Three new deletion mutants and an insertion mutant of E. coli bacteriophage P2, del2, vir79, del4 and sig5, were mapped by the electron microscope heteroduplex method. The deletions were found to cover 45.5-51.6%, 75.6-76.7% and 92.3-99.3% respectively of P2 DNA while sig5 represented a 3.7% insertion at 78.6% from the left end. The region covering 75.9-76.7% of P2 DNA is also deleted in the two previously characterized immunity insensitive variants of P2, vir22 and Hy dis. This region may identify the portion of the genome responsible for immunity. The physical and genetic maps of P2 were previously found to be colinear with respect to the two mutations vir22 and vir37. This relationship is confirmed by the position of del2.