DNA of Bacillus subtilis bacteriophage SPP1: physical mapping and localization of the origin of replication

Abstract

The genome of B. subtilis bacteriophage SPP1, a linear, 28.5-megadalton DNA duplex, was mapped by analysis with the restriction endonuclease endo R.Sal I, Sma I, Xba I, Bgl I, Bgl II and EcoRI. The SPP1 genome, like that of the Salmonella typhimurium phage, P22, was a terminally repetitious, circularly permuted molecule. 6-(p-Hydroxyphenylazo)uracil, a selective, reversible inhibitor of SPP1 DNA synthesis, was exploited to synchronize the initiation of genome replication and to selectively label the site of its initiation with radioactive thymidine. Restriction endonuclease analysis of the distribution of the label located the origin of replicative synthesis at an area about 0.2 genome length from one moleculr terminus.