FIG 6.

Working model for the BfmRS two-component system regulatory circuit. Phosphorylated BfmR (BfmR∼P) binds to promoter regions to activate transcription of the general stress response genes. BfmR can autophosphorylate using small molecule phosphodonors, such as acetylphosphate and carbamoylphosphate. BfmS represses BfmR∼P activation of stress-related genes by dephosphorylating BfmR. The signal that BfmS responds to is unknown. Unphosphorylated BfmR can also bind DNA, but this does not induce transcription of the genes we tested, and thus the role of unphosphorylated BfmR is yet to be determined.