The Staphylococcus aureus Alternative Sigma Factor ς B Controls the Environmental Stress Response but Not Starvation Survival or Pathogenicity in a Mouse Abscess Model

Abstract

The role of ς B , an alternative sigma factor of Staphylococcus aureus , has been characterized in response to environmental stress, starvation-survival and recovery, and pathogenicity. ς B was mainly expressed during the stationary phase of growth and was repressed by 1 M sodium chloride. A sigB insertionally inactivated mutant was created. In stress resistance studies, ς B was shown to be involved in recovery from heat shock at 54°C and in acid and hydrogen peroxide resistance but not in resistance to ethanol or osmotic shock. Interestingly, S. aureus acquired increased acid resistance when preincubated at a sublethal pH 4 prior to exposure to a lethal pH 2. This acid-adaptive response resulting in tolerance was mediated via sigB . However, ς B was not vital for the starvation-survival or recovery mechanisms. ς B does not have a major role in the expression of the global regulator of virulence determinant biosynthesis, staphylococcal accessory regulator ( sarA ), the production of a number of representative virulence factors, and pathogenicity in a mouse subcutaneous abscess model. However, SarA upregulates sigB expression in a growth-phase-dependent manner. Thus, ς B expression is linked to the processes controlling virulence determinant production. The role of ς B as a major regulator of the stress response, but not of starvation-survival, is discussed.