SPP1 DNA replicative forms: growth of phage SPP1 in Bacillus subtilis mutants temperature-sensitive in DNA synthesis.

The development of bacteriophages SPP1 and phi 29 has been studied in several B. sutilis mutants defective in host DNA replication, under non permissive conditions. Several gene products, involved in the synthesis of host DNA, are required for phi 29 replication, while SPP1 seems to require only the host DNA polymerase III. In addition both phages are unable to grow in a dna A mutant (ribonucleotide reductase). Taking advantage of the fact that SPP1 DNA is actively replicated in several dna mutants at non-permissive temperature, we have studied the structure of the replicative intermediates of this phage in the absence of interfering host DNA synthesis. Fast sedimenting forms of SPP1 DNA can be isolated from phage infected cells and evidence of covalently joined concatemers has been obtained, suggesting the presence of terminally repeated sequences.