| Project/Area Number |
09670279
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Bacteriology (including Mycology)
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NISHIBUCHI Mitsuaki Kyoto University, Center for Southeast Asian Studies, Professor, 東南アジア研究センター, 教授 (50189304)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1997: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | Vibrio parahaemolyticus / hemolysin / Kanagawa phenomenon / promoter / base change / ヘモリシン / 毒素 / プロモーター活性 / 溶血毒遺伝子 / ミニドランスポゾン / 部位特異的変異 |
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| Research Abstract |
The tdh (thermostable direct hemolysin) and trh (tdh-ralated hemolysin) genes are considered major virulence genes of Vibrio parahaemolyticus. Only Kanagawa phenomenon (KP) positive strains exhibiting strong beta-type hemolysis used to be considered virulent strains. These strains carry two tdh genes (tdh1, tdh2). However, KP negative strains lacking the tdh gene has recently been isolated often from clinical sources in Asia. Some of the strains were found to carry the trh gene. We also found the same tendency with the stains isolated in the United States. Many trh-positive strains also carried the tdh gene and the tdh expression in these strains was lower than that of KP-positive strains. Very recently, we found that a new clone of the O3 : K6 strains has caused a pandemic. The O3 : K6 strains carried the tdh gene only and were KP positive, and the level of tdh expression was similar to that of classical KP-positive strains. Of all the tdh genes, including tdh3 to tdh5 genes cloned from KP-negative strains, only the tdh2 was transcribed at a high level and thus contributed to KP.The other tdh genes had one important base mutation in their promoter sequences. When the base was changed to the base corresponding to that of the tdh2 gene, the tdh genes with promoter mutation contributed to KP.The one-base promoter mutation can be induced under a selective pressure in vivo, and thus the KP-negative but tdh-positive strains are considered clinically significant. Transcription of the trh gene is much lower than that of the tdh2 gene. It is important to examine in a future study whether trh transcription can be increased under a certain condition.
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