Comprehensive Characterization of the Contribution of Individual SigB-Dependent General Stress Genes to Stress Resistance ofBacillus subtilis

Publisher Website
Google Scholar
Abstract
TheσB-dependent general stress regulon ofBacillus subtiliscomprises more than 150 members. Induction of this regulon by imposition of environmental or metabolic stress confers multiple, nonspecific, and preemptive stress resistance to nongrowing, nonsporulated cells ofB. subtilis. In this study we performed a regulon-wide phenotypic screening analysis to determine the stress sensitivity profiles of 94 mutants defective in candidate members of the general stress regulon that were previously identified in our transcriptional profiling study of the general stress response ofB. subtilis. The phenotypic screening analysis included analysis of adaptation to a growth-inhibiting concentration of ethanol (10%, vol/vol) or NaCl (10%, wt/vol), severe heat shock (54°C), and low temperature (survival at 4°C and growth at 12.5°C). Surprisingly, 85% of the mutants tested displayed increased sensitivity at an α confidence level of ≤0.01 to at least one of the four stresses tested, and 62% still exhibited increased sensitivity at anα of ≤0.001. In essence, we were able to assign 63 genes (28 genes with an α of ≤0.001) to survival after ethanol shock, 37 genes (28 genes with an α of ≤0.001) to protection from NaCl shock, 34 genes (24 genes with an α of≤ 0.001) to survival at 4°C, and 10 genes (3 genes with an α of ≤0.001) to management of severe heat shock. Interestingly, there was a substantial overlap between the genes necessary for survival during ethanol shock and the genes necessary for survival at 4°C, and there was also an overlap between genes required for survival during ethanol shock and genes required for survival during NaCl shock. Our data provide evidence for the importance of the σBregulon at low temperatures, not only for growth but also for survival. Moreover, the data imply that a secondary oxidative stress seems to be a common component of the severe stresses tested.