Expression of the ς B -Dependent General Stress Regulon Confers Multiple Stress Resistance in Bacillus subtilis

Abstract

ABSTRACT The alternative sigma factor ς B of Bacillus subtilis is required for the induction of approximately 100 genes after the imposition of a whole range of stresses and energy limitation. In this study, we investigated the impact of a null mutation in sigB on the stress and starvation survival of B. subtilis. sigB mutants which failed to induce the regulon following stress displayed an at least 50- to 100-fold decrease in survival of severe heat (54°C) or ethanol (9%) shock, salt (10%) stress, and acid (pH 4.3) stress, as well as freezing and desiccation, compared to the wild type. Preloading cells with ς B -dependent general stress proteins prior to growth-inhibiting stress conferred considerable protection against heat and salt. Exhaustion of glucose or phosphate induced the ς B response, but surprisingly, ς B did not seem to be required for starvation survival. Starved wild-type cells exhibited about 10-fold greater resistance to salt stress than exponentially growing cells. The data argue that the expression of ς B -dependent genes provides nonsporulated B. subtilis cells with a nonspecific multiple stress resistance that may be relevant for stress survival in the natural ecosystem.