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Keywords:

  • chemical stress;
  • exponential phase;
  • food preservation;
  • heat;
  • high hydrostatic pressure;
  • pulsed electric fields;
  • sigB;
  • sublethal damage;
  • S. aureus

Abstract

Aims:  To examine the role of the alternative general stress sigma factor σB on the resistance of Staphylococcus aureus to stresses of relevance to food preservation, with special emphasis on emerging technologies such as pulsed electric fields (PEF) and high hydrostatic pressure (HHP).

Methods and Results: S. aureus strain Newman and its isogenic ΔsigB mutant were grown to exponential and stationary growth phases and its resistance to various stresses was tested. The absence of the σB factor caused a decrease in the resistance to heat, PEF, HHP, alkali, acid and hydrogen peroxide. In the case of heat, the influence of the σB factor was particularly important, and decreases in decimal reduction time values of ninefold were observed as a result of its deficiency. The increased thermotolerance of the parental strain as compared with the sigB mutant could be attributed to a better capacity to sustain and repair sublethal damages caused by heat.

Conclusions:  σB factor provides S. aureus cells with resistance to multiple stresses, increasing survival to heat, PEF and HHP treatments.

Significance and Impact of the Study:  Results obtained in this work help in understanding the physiological mechanisms behind cell survival and death in food-processing environments.