| Summary: | 碩士 === 國立中興大學 === 化學系所 === 97 === Erwinia carotovora subsp. carotovora is a phytopathogenic enterobacterium responsible for the soft-rot disease of many plants species. In spite of economic importance, there is no efficient method has been found to control this disease. The low-molecular-weight bacteriocin is an antibiotic that inhibit the growth of closely related bacteria . In this study, we show a newly bacteriocin that be found from E.c.c.
The strain Rif-T06 produces low-molecular-weight bacteriocin(LMWB) to inhibit the growth of indicator strain 95F-3. The transposon Tn5, which harboring drug-resistance marker, was integrated into the genomic DNA of the host cell Rif-T06. Out of the 10000 colonies of possible mutants, 14 colonies were obtained that could not produce LMWB. The TAIL-PCR technology was used to amplify unknown DNA fragments from the Tn5 transposon. TT6-13 was a Tn5 insertional mutant strain, and it has not expressed LMWB. After sequencing, a DNA fragment of 2750 base pair was determinated. It shows that there two complete open reading frames(ORF1 and ORF2) in the Tn5 interrupted gene, and Tn5 was located in ORF1 between 1274-bp and 1275-bp. The 2750-bp gene, named carocin S3 gene, consists of caroS3K(ORF1) and caroS3I(ORF2). Deduction of amino acid sequence, the homology of carocin S3 was similar to the colicin D(24％), which has ribonuclease activity. The construct pGS3K, which contains the carocin S3 gene, has produced bacteriocin activity in E.c.c. TT6-13 and 95F-3 strains.
The carocin S3 can divide into four domains: receptor domain(domain I), unknown domain(domain II), translocation domain(domain III) and killing domain(domain IV). In our previous studies, the carocin S3 is different with carocin S1, and is different with carocin S2 in domain IV. Interestingly, the domain I, domain II and domain III are homologous between carocin S3 and carocin S2. It indicate that has the same translocation modle but different attack way.
|
|---|
