Isolation of new Pseudomonas tolaasii bacteriophages and genomic investigation of the lytic phage BF7

Sixteen lytic bacteriophages that infect Pseudomonas tolaasii LMG 2342T were isolated from smashed sporocarps of oyster mushroom (Pleurotus ostreatus) showing necrotic symptoms. On the basis of the host range investigation of the phages, they have wide infection abilities against the genus Pseudomonas, mainly in the case of phages Bf3, Bf7, Bf10, and Bf15. Molecular investigations have revealed that they all have dsDNA genomes about 40kbp in size. Identical restriction patterns resulting from restriction enzyme analysis suggest that the isolates probably belong to the same phage species. However, there was a difference between these phage isolates in their infecting abilities. Phage isolate Bf7 was investigated and characterized more deeply. Morphological characterization of Bf7 by transmission electron microscopy (TEM) has shown that it has a short, noncontractile tail, an icosahedral phage head, and the size is about 60nm in diameter, suggesting that it belongs to the Podoviridae family. Complete genome sequence analysis of the Bf7 phage isolate revealed a 40058bp genome, 58.4% G+C content, 46 open reading frames encoding different proteins showing homology to proteins of the bacteriophage Caulobacter crescentus fCd1 from the Podoviridae family. On the basis of these results and comparative genomic studies, we classified the Bf7 phage to the subfamily of Autographivirinae, fKMV-like phages.