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Heat resistance, membrane fluidity and sublethal damage in Staphylococcus aureus cells grown at different temperatures

Cebrián, G., Condón, S., Mañas, P.
International journal of food microbiology 2019 v.289 pp. 49-56
Staphylococcus aureus, bacteria, benzyl alcohol, developmental stages, heat, heat tolerance, heat treatment, membrane fluidity, models, temperature
In this work the influence of growth temperature (10–42 °C) on Staphylococcus aureus heat resistance was studied, and its relationship with the ability of cells to repair sublethal damages and with membrane fluidity was evaluated. Non-linear, convex from above survival curves were obtained, and therefore a special case of the Baranyi model was used to fit them. For exponential phase cells, heat resistance did not change with growth temperature in the range between 10 and 37 °C, but cells grown at 42 °C were significantly more resistant, showing D58 and shoulder length (sl58) values 2.5 and 4 times greater than the others, respectively. For stationary growth phase cells, an increase in growth temperature above 20 °C resulted in an increase in D58 values, and cells grown at 42 °C also displayed the highest D58 and sl58 values. The increased heat resistance at 58 °C of stationary growth phase cells grown at higher temperatures was coincident with the appearance of a higher proportion of sublethally damaged cells capable of recovery and outgrowth in non-selective medium. Membrane fluidity was measured at treatment temperatures, and it was observed that those cells with more rigid membranes displayed greater heat resistance (Pearson coefficient = 0.969***). Additionally, S. aureus cells whose membrane was fluidized through exposure to benzyl alcohol were notably sensitized against the action of heat, in a concentration-dependent manner. Results obtained in this research indicate that membrane physical state could be an important factor determining the survival capacity of bacterial cells to a heat treatment.