Expression of a stress- and starvation-induced dps/pexB-homologous gene is controlled by the alternative sigma factor sigma(B) in Bacillus subtilis

sigma(6)-dependent general stress proteins (G:sps) of Bacillus subtilis are essential for the development of glucose-stravation-induced cross-resistance to oxidative challenge. However, the proteins directly involved in this nonspecific resistance to oxidative stress have to be identified. We found that one prominent Gsp displayed strong sequence similarity to the previously characterised oxidative-stress-inducible MrgA protein of B. subtilis and to the starvation-induced Dps/PexB protein of Escherichia coli. We therefore designated this prominent Gsp Dps. While MrgA belongs to the peroxide-stress-inducible proteins needed for the H2O2-inducible adaptive response to oxidative stress, Dps belongs to the proteins induced by heat, salt, or ethanol stress and after starvation for glucose but not by a sublethal oxidative challenge. Primer extension experiments identified two overlapping promoters upstream of the coding region of dps, one being sigma(B) dependent (P-B) and the other being sigma(B) independent (P-1). Both promoters contribute to the basal level of dps during growth. After stress or during entry into the stationary phase, transcription from P-B strongly increased whereas transcription from P-1 decreased. Mutant strains lacking Dps completely failed to develop glucose-starvation-induced resistance to oxidative stress. These results confirm our suggestion that sigma(B)-dependent general stress proteins of B. subtilis are absolutely required for the development of nonspecific resistance to oxidative stress.