Isolation and characterization of a novel filamentous phage from Stenotrophomonas maltophilia

In this study, a novel filamentous phage, phi SHP1, of the environmental Stenotrophomonas maltophilia strain P2 was isolated and characterized. Electron microscopy showed that phi SHP1 resembled members of the family Inoviridae and was about 2.1 mu m long. The 6,867-nucleotide genome of phi SHP1 was a circular single-stranded DNA and had a replication form designated pSH1. Ten putative open reading frames (ORFs) were found in the phi SHP1 genome, and six predicted proteins showed similarity to proteins in databases. Tricine sodium dodecyl sulfate polyacrylamide gel electrophoresis of phi SHP1 displayed one major structural polypeptide of approximately 4.0 kDa. N-terminal sequencing showed that it was the mature product of ORF5 and that its N-terminal 27 amino acid residues had been cleaved off from the predicted nascent protein. Finally, phylogenetic trees were constructed to analyze the phylogenetic relationship of phi SHP1 to other known filamentous phages. phi SHP1 appears to be the first reported Stenotrophomonas filamentous phage.