Role of Stress Response Genes in Resistance and Germination of Bacillus subtilis Spores.

Bacterial adaptation to hostile environments depends on the coordinated expression of stress response genes. When adverse conditions persist and nutrients become limiting, sporulating species may initiate sporulation as a last-resort survival strategy. However, sporulation under such conditions may alter the resistance and germination properties of the resulting spores. In this study, we investigated whether stress response regulators that facilitate vegetative cell adaptation to temperature and/or salinity changes during growth can influence the properties of Bacillus subtilis 168 spores. To this end, we examined the resistance and germination of mutant spores lacking key regulators of stress response pathways (SigB, SigW, SigX, Fur, HrcA, CtsR, and CssRS regulon), all produced under optimal sporulation conditions. The constitutive activation of the SigB-mediated general stress response, achieved through the deletion of its negative regulator RsbX, reduced spore heat resistance by 2.2-fold compared to the parental strain, while no effect was observed in vegetative cells. Additionally, ΔrsbX spores displayed both impaired nutrient-induced and CaDPA-induced germination. Collectively, these findings suggest that stress response regulators can influence spore behavior, although their effects may differ from those observed in vegetative cells.