title: Escherichia coli heat shock protein DnaK: production and consequences in terms of monitoring cooking.
abstract: Through use of commercially available DnaK proteins and anti-DnaK monoclonal antibodies, a competitive enzyme-linked immunosorbent assay was developed to quantify this heat shock protein in Escherichia coli ATCC 25922 subjected to various heating regimens. For a given process lethality (F(70)(10) of 1, 3, and 5 min), the intracellular concentration of DnaK in E. coli varied with the heating temperature (50 or 55 degrees C). In fact, the highest DnaK concentrations were found after treatments at the lower temperature (50 degrees C) applied for a longer time. Residual DnaK after heating was found to be necessary for cell recovery, and additional DnaK was produced during the recovery process. Overall, higher intracellular concentrations of DnaK tended to enhance cell resistance to a subsequent lethal stress. Indeed, E. coli cells that had undergone a sublethal heat shock (105 min at 55 degrees C, F(70)(10) = 3 min) accompanied by a 12-h recovery (containing 76,786 +/- 25,230 molecules/cell) resisted better than exponentially growing cells (38,500 +/- 6,056 molecules/cell) when later heated to 60 degrees C for 50 min (F(70)(10) = 5 min). Results reported here suggest that using stress protein to determine cell adaptation and survival, rather than cell counts alone, may lead to more efficient heat treatment.
authors.affiliation: Food Research and Development Centre, Agriculture and Agri-Food Canada, Saint-Hyacinthe, Québec J2S 8E3, Canada.
authors.forename: Karine
authors.initials: K
authors.lastname: Seyer
authors.forename: Martin
authors.initials: M
authors.lastname: Lessard
authors.forename: Gabriel
authors.initials: G
authors.lastname: Piette
authors.forename: Monique
authors.initials: M
authors.lastname: Lacroix
authors.forename: Linda
authors.initials: L
authors.lastname: Saucier
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D015169:Colony Count, Microbial; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000254:growth & development* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000276:immunology / Q000378:metabolism*; D018869:Heat-Shock Response; D006358:Hot Temperature
chemical_list: D000911:Antibodies, Monoclonal; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; C063842:dnaK protein, E coli