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 σB-dependent induction of spo0E, encoding a phosphatase specifically inactivating the sporulation master regulator Spo0A∼P. Here we show that the σB promoter (PσB) of spo0E is responsive to sub-inhibitory levels of ethanol stress, producing a σB-dependent sporulation deficient phenotype. In addition to positive regulation by σB, we identified Rok, the repressor of comK, to be a direct repressor of spo0E expression from PσB. This constellation provides the possibility to integrate signals negatively acting on sporulation initiation through the σB branch as well as a positive feedback loop acting on PσB 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.
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