| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1999: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
φCTX is a cytotoxin-converting phage isolated from Pseudomons aeruginosa. In this study, we determined the complete nucleotide sequence of φCTX phage genome. The precise genome size was 35,538 bp. Forty seven ORFs were identified on the φCTX genome, including two previously identified genes, ctx and int. Among them, fifteen gene products were identified in the phage particle. The most striking feature of the φCTX genome was an extensive homology with the coliphage P2 and P2-related phages; more than half of the ORFs had marked homology to P2 genes. The gene arrangement on the genome was also highly conserved for the two phages, though the G+C content and codon usage of most φCTX genes were similar to those of the host P. aeruginosa chromosome. In addition, φCTX was found to share several common features with P2, including the morphology, non-inducibility, use of LPS core oligosaccharide as receptor and CaィイD22+ィエD2-dependent receptor binding. These findings indicate that φCTX is a P2-l
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ike phage well adapted to P. aeruginosa, and provide a clear evidence of the intergeneric spread and evolution of bacteriophages. Furthermore, comparative analysis of genome structures of φCTX, P2 and other P2-relatives revealed the presence of several hot spots where foreign DNAs, including the cytotoxin gene, were inserted. They appear to be deeply concerned in the acquisition of various genes that are horizontally transferred by bacteriophage infection.
Pseudomonas aeruginosa produces three types of bacteriocins; R-type, F-type, and S-type pyocins. The S-type pyocin is a simple colicin-like protein, whereas the R-type resembles a contractile tail structure of bacteriophage, and the F-type a non-contractile tail of bacteriophage. Since φCTX is a member of R pyocin-related phages which are genetically and serologically related to R pyocin, above-mentioned results suggested the relatedness of R pyocin to the P2 phage family. Thus, the nucleotide sequence of R2 pyocin genes, along with those for F2 pyocin which are located downstream of the R2 gene cluster on the chromosome of P. aeruginosa PAO1, was analyzed in order to elucidate the relationship between the pyocins and bacteriophages. Further, in order to specify the R2 pyocin locus, we determined the nucleotide sequence of the corresponding region of the strain PML14 which produced only F2 pyocin. The results clearly demonstrated that the R-type pyocin is derived from a common ancestral origin with the P2 phage family and the F-type from the λ phage family. This notion was supported by identification of a lysis gene cassette similar to those for bacteriophages. The gene organization of the R2 and F2 pyocin gene cluster, however, suggested that the both pyocins are not simple defective phages but are phage tails that have been evolutionarily specialized as bacteriocins. Less
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