Role of sigB and osmolytes in desiccation survival of Listeria monocytogenes in simulated food soils on the surface of food grade stainless steel

Yannan Huang, Timothy C. Ells, Lisbeth Truelstrup Hansen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

This research aimed to determine whether the SigB (sigma(B)) regulon and osmolytes impact the survival of the foodborne pathogen, Listeria monocytogenes, during desiccation in simulated food soils with varying salt and nutrient contents on food grade stainless steel (SS) surfaces. L. monocytogenes 568 (Lm568, serotype 1/2a), its isogenic sigB mutant (Delta sigB) and the back-complemented Delta sigB were desiccated in BHI, TSB with 1% glucose (TSB-glu), peptone physiological saline (PPS) and minimal media (MM) for 21 days at 43% relative humidity (RH) and 15 degrees C on SS. The effect of food related osmolytes (proline, betaine and carnitine) on desiccation survival was studied by (a) pre-culturing strains in MM with an osmolyte followed by desiccation in MM and (b) by desiccating strains in MM with an osmolyte. Desiccation survival of L. monocytogenes was positively correlated to the nutrient and osmolyte concentrations in the desiccation substrates. Initial Lm568 levels of 8 Log(CFU/cm(2)) decreased by 0.9 Log(CFU/cm(2)) in BHI and 1.1-2.9 Log(CFU/cm(2)) in TSB-glu, PPS and MM after 21 days. Comparatively, the initial survival of Delta sigB was reduced in PS and MM, while no differences were observed among the three strains in BHI and TSB-glu. Pre-culture in osmolyte containing MM enhanced (p <0.05) desiccation survival of all strains. Desiccation in osmolyte-containing MM improved desiccation survival of all strains, albeit the protection was less than that observed after pre-culture with the osmolytes. Complementation of the Delta sigB mutant restored the wildtype phenotype. In conclusion, this work shows the protective effect of osmolytes in desiccation survival of L. monocytogenes, while the sigma(B) regulon only improved the initial survival in nutrient and osmolyte poor environments. (C) 2014 Elsevier Ltd. All rights reserved.
Original languageEnglish
JournalFood Microbiology
Volume46
Pages (from-to)443-451
ISSN0740-0020
DOIs
Publication statusPublished - 2015
Externally publishedYes

Keywords

  • Listeria monocytogenes
  • Desiccation stress
  • Osmotic stress
  • SigB regulon
  • Osmolytes
  • Salt
  • Stainless steel
  • Stress response

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