title: Identification of factors involved in recovery of heat-injured Salmonella Enteritidis.
abstract: Proteins and genes involved in the recovery of heat-injured Salmonella Enteritidis were investigated. Salmonella Enteritidis cells cultured overnight in tryptic soy broth (TSB; nonselective medium) were suspended in citric acid-disodium hydrogen phosphate buffer (pH 6). After heat treatment at 55 degrees C for 15 min, the culturable counts measured by tryptic soy agar (TSA; nonselective 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 Salmonella Enteritidis detected on TSA were injured but recoverable. When injured Salmonella Enteritidis was incubated in TSB, the culturable count measured by TSA did not increase for 2 h, whereas that by DHL agar increased after incubation for 30 min. After incubation for 2 h, the culturable count measured by DHL agar reached a similar level with that by TSA, indicating that Salmonella Enteritidis had recovered. The two-dimensional polyacrylamide gel electrophoresis analysis revealed that elongation factor G (FusA) and pyruvate kinase (PykF) specifically increased in the cells just after heat treatment and in the recovery cells. The levels of transcription of 86 stress-inducible genes were also investigated by reverse transcription PCR. Nineteen heat-inducible (clpB, clpX, degP, dnaJ, fkpA, ftsJ, gapA, hflB, hslJ, hslU, hslV, htpG, htrA, lon, 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 transcribed extensively during recovery in TSB. The results obtained in this study will be used to develop the media or culture conditions that will promote recovery for the detection of food poisoning bacteria, including injured cells from food products.
authors.affiliation: Laboratory of Food Hygienic Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Takahisa
authors.initials: T
authors.lastname: Miyamoto
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: Madoka
authors.initials: M
authors.lastname: Kiriki
authors.forename: Ai
authors.initials: A
authors.lastname: Motomatsu
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Honjoh
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Iio
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry*; D001483:Base Sequence; D015169:Colony Count, Microbial; D003470:Culture Media; D004587:Electrophoresis, Agar Gel / Q000379:methods; D005516:Food Microbiology; D006358:Hot Temperature / Q000009:adverse effects*; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012477:Salmonella enteritidis / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media