Cross-talk between the general stress response and sporulation initiation in Bacillus subtilis - the σ(B) promoter of spo0E represents an AND-gate.

The general stress response and the decision-making processes of sporulation initiation are interconnected pathways in the regulatory network of Bacillus subtilis. In a previous study we provided evidence for a mechanism capable of impairing sporulation by σ(B) -dependent induction of spo0E, encoding a phosphatase specifically inactivating the sporulation master regulator Spo0A~P. Here we show that the σ(B) promoter (Pσ(B)) of spo0E is responsive to sub-inhibitory levels of ethanol stress, producing a σ(B) -dependent sporulation deficient phenotype. In addition to positive regulation by σ(B) , we identified Rok, the repressor of comK, to be a direct repressor of spo0E expression from Pσ(B) . This constellation provides the possibility to integrate signals negatively acting on sporulation initiation through the σ(B) branch as well as a positive feedback loop acting on Pσ(B) by Rok that is most likely a direct consequence of Spo0A~P activity. Thus, the molecular mechanism described here offers the opportunity for cross-talk between the general stress response and sporulation initiation in the adaptational gene expression network of B. subtilis.