Abstract
Two temperate bacteriophages have been isolated from Bacillus larvae: PBL1 and PBL0.5. Strains lysogenic for either of these phages are immune to lysis by the same phage but are sensitive to the other phage. PBL1 has an oval head, a non-contractile tail, and a base plate with a pin structure but no apparent tail fibres. The genome of PBL1 consists of double-stranded DNA with a molecular weight of 24.1 (±0.6) x 106, a G + C content (derived from melting temperature) of 41.5%, and cohesive ends. Restriction enzyme analysis permitted construction of a physical map of the genome.