Role of the alternative sigma factor sigma on Staphylococcus aureus resistance to stresses of relevance to food preservation

To examine the role of the alternative general stress sigma factor sigma(B) 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). S. aureus strain Newman and its isogenic DeltasigB mutant were grown to exponential and stationary growth phases and its resistance to various stresses was tested. The absence of the sigma(B) 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 sigma(B) 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. sigma(B) factor provides S. aureus cells with resistance to multiple stresses, increasing survival to heat, PEF and HHP treatments. Results obtained in this work help in understanding the physiological mechanisms behind cell survival and death in food-processing environments.