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Permanent link (DOI): https://doi.org/10.7939/R32Z1337G

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Heat and pressure resistance of Escherichia coli Open Access

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Other title
Subject/Keyword
heat resistance
Escherichia coli
meat
locus of heat resistance
antimicrobials
protein aggregation
pressure resistance
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Li, Hui
Supervisor and department
Gänzle, Michael (Agricultural, Food and Nutritional Science)
Examining committee member and department
Temelli, Feral (Agricultural, Food and Nutritional Science)
Ramaswamy, Hosahalli (Food Science, McGill University)
Raivio, Tracy (Biological Sciences)
McMullen, Lynn (Agricultural, Food and Nutritional Science)
Gänzle, Michael (Agricultural, Food and Nutritional Science)
Department
Department of Agricultural, Food, and Nutritional Science
Specialization
Food Science and Technology
Date accepted
2017-05-08T10:28:36Z
Graduation date
2017-11:Fall 2017
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Strains of Escherichia coli may survive heat or pressure stress, acquire specific virulence genes and cause severe human diseases. The locus of heat resistance (LHR) has been identified as an important heat resistant element in E. coli. The objective of this thesis was to explore the role of the LHR on heat and pressure resistance of E. coli, as well as its relationship with protein folding and aggregation, and evaluate the effects of food matrix and antimicrobials on pressure resistance of E. coli. To explore the heat and pressure resistance related to protein folding and aggregation, the role of LHR was investigated in E. coli MG1655 expressing ibpA-yfp fusion. A total 10 proteins of LHR were detected through proteomic analysis using mass spectrometry, including two small heat shock proteins, two heat shock proteases, proteins of the YfdX family, thioredoxin, and a sodium/hydrogen antiporter. Microscopic observations showed that LHR reduced the inclusion bodies after heat or the pressure treatment, indicating that LHR proteins function to re-fold and turnover aggregated proteins. The proteomic analysis confirmed that the phenotype of pressure resistance of LHR occurred through stress regulation, mitigation of protein aggregation and reduction of oxidative stress. To evaluate the effect of food matrix on the pressure resistance of E. coli, the resistance of two five-strain cocktails to pressure in bruschetta, tzatziki, yogurt and ground beef was compared. Pressure reduced E. coli in plant and dairy products by more than 5 logs (cfu/mL) but not in ground beef. Food components calcium, magnesium, glutamate, caffeic acid and acetic acid exhibited a protective effect on E. coli after pressure treatment and during storage at 4 °C. Further study assessed the combined effect of antimicrobials and pressure on enterohaemorrhagic E. coli (EHEC) in pressure treated beef steaks. The thiol-reactive allyl-isothiocyanate (AITC) and cinnamaldehyde exhibited synergistic activity with pressure on E. coli. However, the membrane-active essential oil components carvacrol and thymol showed antagonistic or no synergistic effect with pressure. In conclusion, the LHR confers pressure resistance of E. coli, and the resistance is related to protein folding and aggregation. Moreover, pressure resistance of E. coli is affected by food matrix and antimicrobials.
Language
English
DOI
doi:10.7939/R32Z1337G
Rights
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
Citation for previous publication
Li, H., and Gänzle, M. (2016). Some like it hot: hear resistance of Escherichia coli in Food. Frontiers in Microbiology, 7, 1763.Li, H., Garcia-Hernandez, R., Driedger, D., McMullen, L.M., Gänzle, M. (2016). Effect of the food matrix on pressure resistance of Shiga-toxin producing Escherichia coli. Food Microbiology. 57, 96-102.Li, H., and Gänzle, M. (2016). Effect of hydrostatic pressure and antimicrobials on survival of Listeria monocytogenes and enterohaemorrhagic Escherichia coli in beef. Innovative Food Science and Emerging Technologies. 38, 321-327.

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