| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
Proteins and genes involved in the recovery of the heat-injured S.Enteritidis were investigated. S.Enteritidis cells cultured overnight in Tryptic Soy Broth (TSB, non-selective medium) were suspended in citric acid-disodium hydrogen phosphate buffer (pH 6). After heat treatment at 55℃ for 15 min, the culturable counts measured by Tryptic Soy Agar (TSA, non-selective medium) decreased from 10^8 to 10^7 CFU/ml. On the other hand, culturable counts measured by Desoxycholate-Hydrogen sulfite-Lactose (DHL) agar (selective medium) were decreased from 10^8 to 10^4 CFU/ml by the same treatment. The results suggest that 99.9% of S.Enteritidis detected on TSA were injured but recoverable. When injured S.Enteritidis was incubated in TSB, the culturable count measured by TSA did not increase until 2 hr, whereas that by DHL agar increased after the incubation for 30 min. After incubation for 2 hr, the culturable count measured by DHL agar reached a similar level with that by TSA, indicating that S. Enteritidis had recovered. The 2D-PAGE analysis revealed that elongation factor G (FusA) and pyruvate kinase (PykF) specifically increased in the cells just after heat treatment and in the recovering cells. The levels of transcription of 86 stress-inducible genes were also investigated by RT PCR. Nineteen heat-inducible (clpB, clpX, degP, dnaJ, fkpA, ftsJ, gapA, hflB, hslJ, hslU, hslV, htpG, htrA, Ion, mopA, mopB, mreB, rpoE and ppiD), and 12 oxidative-stress and DNA-damage-inducible (ahpC, ahpF, fldB, fur, grxA, dinF, katG, mutM, recA, soxR, trxC and zwf) genes were extensively transcribed during recovery in TSB. The results obtained in this study will be used to develop the media or culture condition that will promote the recovery for the detection of food-poisoning bacteria including injured cells from food products.
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