| Summary: | High hydrostatic pressure (HHP) is a widely accepted nonthermal technology for ensuring food safety without compromising nutritional values and organoleptic properties. This study investigated the survival and molecular responses of Escherichia coli O157:H7 when it was subjected to HHP. The inactivation of E. coli O157:H7 by HHP was observed at 250 MPa and higher pressures (p < 0.05), but not at 50 MPa and 150 MPa. Whole transcriptome sequencing (RNA-seq) revealed the underlying adaptive responses of E. coli O157:H7 induced by the slightly elevated pressure. Under 50 MPa HHP, twenty-two genes were differentially expressed, and seventeen of these genes were upregulated to maintain normal cell functions. In comparison, most of the differentially expressed genes were downregulated with higher HHP (150 MPa and 250 MPa) treatment, indicating impaired cellular activities. The effectiveness of HHP-based bacterial cell inactivation demonstrated a pressure-dependent manner. Appropriate HHP levels used in bacterial inactivation should be carefully determined for eliminating pathogenic E. coli without induction of the resistance of the food-processing-related stresses.
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