Cross-talk between the general stress response and sporulation initiation in Bacillus subtilis - the sB 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 sB-dependent induction of spo0E, encoding a phosphatase specifically inactivating the sporulation master regulator Spo0A similar to P. Here we show that the sB promoter (PsB) of spo0E is responsive to sub-inhibitory levels of ethanol stress, producing a sB-dependent sporulation deficient phenotype. In addition to positive regulation by sB, we identified Rok, the repressor of comK, to be a direct repressor of spo0E expression from PsB. This constellation provides the possibility to integrate signals negatively acting on sporulation initiation through the sB branch as well as a positive feedback loop acting on PsB by Rok that is most likely a direct consequence of Spo0A similar to 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.