碩士 / 國立成功大學 / 微生物及免疫學研究所 / 98 / Vibrio vulnificus, a gram-negative estuarine bacterial species, is pathogenic to humans and eels. Only a fraction of V. vulnificus strains, classified as biotype (BT) 2, is virulent for the eel, and the virulence is conferred by a common plasmid in the BT2 strains. It has been shown previously that the BT2 virulence plasmid, though itself is not transmissible, could be transferred between the BT2 strains with a frequency of about 10-2 in the presence of a conjugative plasmid found in most of BT2 strains. In this study, we investigated the transmissibility of a BT2 virulence plasmid, pR99 possessed by strain CECT4999, to three clinical BT1 strains, SW058, SW059 and YJ016, and three environmental BT1 isolates, CG024, CG027 and CG028. The plasmids pR99 and pC4602-1, a BT2 conjugative plasmid, were inserted with chloramphenicol- and ampicillin-resistance cassettes, respectively, for the selection of transconjugants with either or both plasmids. The results indicate that pR99 could be transferred from a BT2 strain into both environmental and clinical BT1 isolates. The frequency of transferring pR99 alone or both pR99 and pC4602-1 were about 10-5~10-6 except for CG024, CG028 and SW059, which showed a frequency of about 10-3. The role of restriction modification systems in preventing uptake of the BT2 plasmid pC4602-1 by the BT1 strains has been excluded as the conjugation frequency of transferring this plasmid from the transconjugant of strain YJ016 back to YJ016 was not elevated. Compared to the BT2 strain, CECT4999, the pR99-possessing BT1 derivatives were only partially resistant to eel serum killing effect. The copy number of pR99 and the mRNA level of vep07, a gene in pR99 that confers the resistance to eel serum, in the BT1 transconjugants were similar to those in strain CECT4999. However, some transconjugants expressed much less Vep07 than strain CECT4999 on the outer membrane while the others expressed similar amount of Vep07 to that of CECT4999. In addition, deletion of vep07 in BT1 transconjugants HC131 and HC147 did not affect the resistance of these two strains to eel serum. These results suggest that Vep07 may not be associated with the resistance of BT1 transconjugants to eel serum killing effect.
| Identifer | oai:union.ndltd.org:TW/098NCKU5380077 |
| Date | January 2010 |
| Creators | Chih-YuHuang, 黃智郁 |
| Contributors | Lien-I Hor, 何漣漪 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 69 |
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