The genome of Bacillus subtilis phage SPP1: the arrangement of restriction endonuclease generated fragments.

SPP1 DNA was cleaved by the restriction endonucleases, BglI, BglII, EcoRI, KpnI, SmaI, and SalI. The molecular weights of the DNA fragments obtained by single enzyme digestion or by consecutive digestion with two enzymes were determined by electron microscopic measurements of contour length and by gel electrophoresis. The major fragments from the six digests could be ordered to give a consistent restriction map of SPP1. The electropherograms of several digests indicated that certain fragments occurred in less than stoichiometric amounts or were heterogeneous in size. Such bands carried a major part of radioactivity, when SPP1 DNA was terminally labelled with P32 prior to degradation by restriction enzymes. These results, and studies of the effect of exonuclease III treatment on restriction enzyme patterns define the terminal restriction fragments. All data obtained support the conclusion drawn in the preceding paper (Morelli et al., 1978 b) that the SPP1 genome is terminally redundant and partially circularly permuted.