Isolation and characterization of bacteriophage PhiBP from Paenibacillus polymyxa CCM 7400.

A bacteriophage PhiBP infecting Paenibacillus polymyxa CCM 7400 was isolated from culture lysate. Electron microscopy of lysate samples revealed the presence of bacteriophage particles with polyhedral heads 56 nm in diameter and flexible noncontractile tails 144 nm in length. The profile of PhiBP structural proteins resembles that of other bacteriophages. The PhiBP genome consists of double-stranded DNA of 43-kbp size. Homology search of sequenced DNA fragments from EcoRI digest revealed regions with significant similarity to other known bacteriophage genes. Regions similar to phage terminase genes were identified within the 1.2-kbp fragment. Three lytic genes, two holin genes and one endolysin gene were identified within the 2.5-kbp fragment. We tested the isolates of P. polymyxa CCM 7400 for the presence of phage DNA on bacterial chromosome using PCR amplification with primers derived from proposed terminase and holin gene sequences. We confirmed the presence of PhiBP DNA on P. polymyxa chromosome by Southern hybridization. The bacteriophage PhiBP was capable of causing lysis of a P. polymyxaPhiBP lysogen despite the presence of the phage DNA on bacterial chromosome. Therefore, we concluded that PhiBP was a virulent mutant phage.