Effect of High Hydrostatic Pressure on Stress-Related , , and Expression Patterns in Selected Strains.

Lactic acid bacteria (LAB) in the natural environment meet multiple stressors such as pH and temperature variations, increased nutrition and metabolite concentrations, harmful chemicals, acidic/oxidative conditions, osmotic pressure, and starvation. However, LAB strains are not subjected to high hydrostatic pressure (HHP) which currently is the most common non-thermal decontamination technology in the food industry. In this context, the LAB response to HHP is more difficult to identify compared to other stress-induced responses, and , , and can serve as essential regulators in this reaction. In the present study, the expression level of , , and mRNAs in 15 LAB strains after the HHP (300 MPa/5') exposure was evaluated. As a result, the HHP-treatment affected the up-regulation of , , and in KKP 3565, KKP 3566, KKP 3570, KKP 3575 strains, whereas, in KKP 3569, KKP 3571, KKP 3573 all genes were lower expressed. The relative expression level of the , , and either before or after the pressure treatment for DSM 6235, KKP 3572, KKP 3574, KKP 3576, KKP 3577, KKP 3578 strains were undetectable. Significant differences in the expression levels were observed, between the control and the HHP treatment strains for in KKP 3565, KKP 3566, KKP 3569, KKP 3570, KKP 3571, in, KKP 3565, KKP 3570, KKP 3571, and in KKP 3569, KKP 3571. Overall, the studied genes, , , and can be useful markers to indicate the LAB cellular response to HHP. These molecular parameters can help to optimize the desirable LAB growing conditions in industrial processes and to understand the complexity of the stress-related mechanism.