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Applied and Environmental Microbiology, June 2003, p. 3231-3237, Vol. 69, No. 6
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.6.3231-3237.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Escherichia coli Heat Shock Protein DnaK: Production and Consequences in Terms of Monitoring Cooking

Karine Seyer,^1,2 Martin Lessard,³ Gabriel Piette,¹ Monique Lacroix,² and Linda Saucier^1*

Food Research and Development Centre, Agriculture and Agri-Food Canada, Saint-Hyacinthe, Québec J2S 8E3,¹ INRS-Institut Armand Frappier, Laval, Québec H7V 1B7,² Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada, Lennoxville, Québec J1M 1Z3, Canada³

Received 13 September 2002/ Accepted 18 March 2003

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 (F₇₀¹⁰ of 1, 3, and 5 min), the intracellular concentration of DnaK in E. coli varied with the heating temperature (50 or 55°C). In fact, the highest DnaK concentrations were found after treatments at the lower temperature (50°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°C, F₇₀¹⁰ = 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°C for 50 min (F₇₀¹⁰ = 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.

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* Corresponding author. Mailing address: Meat Industry Section, Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Blvd. West, Saint-Hyacinthe, Québec, Canada J2S 8E3. Phone: (450) 773-1105. Fax: (450) 773-8461. E-mail: saucierl{at}agr.gc.ca.

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Applied and Environmental Microbiology, June 2003, p. 3231-3237, Vol. 69, No. 6
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.6.3231-3237.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

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