Characterization of Inducible Bacteriophages in Bacillus licheniformis

Abstract

Two morphologically distinct and physically separable defective phages have been found in Bacillus licheniformis NRS 243 after induction by mitomycin C. One of them (PBLB) is similar to the defective phage PBSX of B. subtilis , which has a density of 1.373 g/cm 3 in CsCl and a sedimentation coefficient of 160 S . PBLB incorporates into its head mainly bacterial deoxyribonucleic acid (DNA) which has a sedimentation coefficient of 22 S and a buoyant density in CsCl of 1.706 g/cm 3 . The other phage (PBLA) has a morphology similar to the temperate phage φ105 of B. subtilis ; the head diameter is about 66 nm, and it possesses a long and noncontractile tail. PBLA has a density of 1.484 g/cm 3 in CsCl and the phage-specific DNA, which is exclusively synthesized after induction by mitomycin C, has a density of 1.701 g/cm 3 . PBLA DNA is double-stranded and has a sedimentation coefficient of 36 S , corresponding to a molecular weight of 34 × 10 6 to 35 × 10 6 daltons. The phage DNA has one interruption per single strand, giving single-stranded segments with molecular weights of 13 × 10 6 and 4 × 10 6 daltons. Common sequences between the two phage DNA species and with their host DNA have been demonstrated by DNA-DNA hybridization studies. Both phage particles kill sensitive bacteria. However, all attempts thus far to find an indicator strain to support plaque formation have been unsuccessful.