| Summary: | 碩士 === 國立中興大學 === 分子生物學研究所 === 92 === Eight strains of lytic phages, including SMA1 ~ SMA8, were isolated from 87 strains of S. maltophilia that were isolated from wastewater and catheter-related devices. SMA2, SMA5, and SMA6 could lyse most clinical isolates of S. maltophilia. These phages contain a double-strained DNA genome with a similar restriction pattern. Electron microscopy shows that SMA5 belonges to the family of Myoviridae. Pulsed-field gel electrophoresis shows that SMA5 has a genome of about 250 kb. N-terminal sequencing of four virion proteins reveals that SMA5 is a novel phage. Various S. maltophilia isolates were used for infection with SMA5, and varied degrees of growth inhibition were observed. No significant loss of phage infectivity was observed after storage of crude lysates of SMA5 at 4℃ for 16 months, indicating that SMA5 is stable. In the other way, it was found that 46 out of 87 collected S. maltophilia strains were able to release infective phage particles. DNA sequencing reveals that the genome of SMT13 is circular, with 33,525 nt in size. Forty-three open reading frames (ORFs) were identified on the SMT13 genome. Based on comparative the analysis of sequence conservation, genome organization, and morphology it is believed that SMT13 is similar to P2 and P2-like phages. Electron microscopy of SMT13 confirmed that this phage belonges to Myoviridae. In order to illustrate the phylogenetic relatedness, SMT13, prophage XccP1, prophage XacP1, P2 and P2-like phages were analyzed with programs BLAST, ClustalX, TreeView, TMHMM, Dot plot, SignalP, and GCG. The part of SMT13 genome containing genes coding for structural proteins, assembly proteins, and terminase is highly related to the P2 and P2-like phages. The other part of the SMT13 genome containing genes coding for lysis related proteins, DNA replication related proteins, lysogeny regulators is far related to the P2 and P2-like phages. The phylogenetic relatedness between SMT13 and prophages on the gamma Proteobacteria genome, including Xylella, Xanthomonas, Stenotrophomonas, and Pseudomonas, was further analyzed.
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