Identification and characterization of a stress‐responsive promoter in the macromolecular synthesis operon of Bacillus subtilis

Open Access
Publisher Website
Google Scholar
Abstract
Bacillus subtilis DB1005 is a temperature-sensitive (Ts) sigA mutant. Induction of σA has been observed exclusively in this mutant harbouring extra copies of the plasmid-borne Ts sigA gene transcriptionally controlled by the P1P2 promoters of the B. subtilis macromolecular synthesis (MMS; rpoD or sigA) operon. Investigation of the mechanisms leading to the induction has allowed us to identify a σB-type promoter, P7, in the MMS operon for the first time. Therefore, at least seven promoters in total are responsible for the regulation of the B. subtilis MMS operon, including the four known σA- and σH-type promoters, as well as two incompletely defined promoters. The P7 promoter was activated in B. subtilis after the imposition of heat, ethanol and salt stresses, indicating that the MMS operon of B. subtilis is subjected to the control of general stress. The significant heat induction of P7 in B. subtilis DB1005 harbouring a plasmid-borne Ts sigA gene can be explained by a model of competition between σA and σB for core binding; very probably, the σB factor binds more efficiently to core RNA polymerase under heat shock. This mechanism may provide a means for the expression of the B. subtilis MMS operon when σA becomes defective in core binding.