In spite of the above mentioned efforts in phage study, no temperate phage of S. maltophilia has been reported. In this study, we

isolated a temperate phage of S. maltophilia and designated as Smp131. Since acquisition of external DNA by horizontal gene transfer and gene loss are major driving-forces of bacterial genome evolution and integration and excision of temperate bacteriophages contribute actively to such evolution [16], we deemed it worthy to study this phage. The phage genome was sequenced and sequence analysis revealed that Smp131 is similar to phage P2 and shares high degrees of identity with prophages of Stenotrophomonas selleck inhibitor and xanthomonads. Results and discussion Phage Smp131 is a temperate myophage infecting S. maltophilia In this study, temperate phages were detected by spotting culture supernatants from 86 clinical isolates

of S. maltophilia onto lawns QNZ cost formed separately by all other isolates. The culture supernatant from S. maltophilia strain T13 was observed to cause clearing zones on 3 of the samples (ATCC 13637, BCRC 11901, and T16). Following 3 rounds of single plaque isolation, Smp131 was obtained and used for further study. Less turbid plaques were formed on lawns of strain T16; therefore, this strain was used as the host for phage propagation and indicator host in titering the phage. Cultures of S. maltophilia T13 released from 1 × 104 to 1 × 106 PFU/ml of Smp131 and enough treatment by adding mitomycin C (1 μg/ml) into the cultures produced titers of approximately 7 × 108 PFU/ml. Electron microscopy

showed that Smp131 has an icosahedral head approximately 60 nm in diameter and a contractile tail 100–120 nm in length and 20–30 nm in width (Figure 1), resembling members of Myoviridae phages. Figure 1 Transmission electron micrograph of Smp131. Samples were stained with 2% uranyl acetate. Scale bar represents 50 nm. In SDS-polyacrylamide gel (10%) electrophoresis, phage particles purified by CsCl ultracentrifugation displayed more than 15 distinct buy Small molecule library protein bands, with molecular masses ranging from 16 to 120 kDa, upon staining the gel with Coomassie brilliant blue. Four bands, with molecular masses of 44, 39.5, 38, and 21 kDa, were more abundant than the others. The 38-kDa protein was the most abundant and is likely the major capsid protein. Host range testing showed that only the three S. maltophilia strains, ATCC 13637, BCRC 11901, and T16, were sensitive to Smp131 as indicated by the formation of single plaques. Several reasons are possible for the phage resistance, including immunity, impaired adsorption and block at later stages during phage infection, and further study is needed to test these possibilities. With such a narrow host range, Smp131 apparently has limited use in control of S. maltophilia infection. Spot tests and plaque assays were also tested on bacteria other than S.