The effect of culture growth phase on induction of the heat shock response in Yersinia enterocolitica and Listeria monocytogenes

• Published in: Journal of applied microbiology Vol. 89; no. 2; pp. 198 - 206
• Main Authors: McMahon, C.M.M., Byrne, C.M., Sheridan, J.J., McDowell, D.A., Blair, I.S., Hegarty, T.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-08-2000; Blackwell Science; Oxford University Press
• Subjects: Biological and medical sciences; Colony Count, Microbial; Culture Media; Food industries; Food microbiology; Fundamental and applied biological sciences. Psychology; Heat-Shock Response; Hot Temperature; Listeria monocytogenes; Listeria monocytogenes - growth & development; Listeria monocytogenes - physiology; Yersinia enterocolitica; Yersinia enterocolitica - growth & development; Yersinia enterocolitica - physiology; Growing phase; Induction; Listeria monocytogenes; Foodstuff; Recovery; Yersinia enterocolitica; Thermal resistance; Thermal shock; Pathogenic; Food preservation; Microorganism culture; Bacteria; Biological contamination; Enterobacteriaceae
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1046/j.1365-2672.2000.01097.x

The effect of culture growth phase on induction of the heat shock response in Yersinia enterocolitica and Listeria monocytogenes, was examined. Exponential or stationary preconditioned cultures were heat shocked and survivor numbers estimated using selective and overlay/resuscitation recovery techniques. The results indicate that prior heat shock induced increased heat resistance in both micro‐organisms to higher heat treatments. Heat‐shocked cells of each micro‐organism were able to survive much longer than non‐heat‐shocked cells when heated at 55 °C. The size of the change in heat resistance between heat‐shocked and non‐heat‐shocked cells was greatest for exponential cultures (X:X). Results indicate that the overall relative thermal resistance of each pathogen was dependent on cell growth phase. Stationary cultures (S:S) were significantly (P < 0·01) more thermotolerant than exponential cultures (X:X) under identical processing conditions. Under most conditions, the use of an overlay/resuscitation recovery medium resulted in higher D‐values (P < 0·05) compared with a selective recovery medium.