Blue Light Activates the σ ^B -Dependent Stress Response of Bacillus subtilis via YtvA

Here we present evidence for a physiologically relevant light response mediated by the LOV domain-containing protein YtvA in the soil bacterium Bacillus subtilis . The loss and overproduction of YtvA abolish and enhance, respectively, the increase in σ B -controlled ctc promoter activity at moderate light intensities. These effects were absent in the dark and in red light but present under blue-light illumination. Thus, activation of the general stress response in B. subtilis is modulated by blue light.