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. Author manuscript; available in PMC: 2019 Nov 1.
Published in final edited form as: Mol Microbiol. 2018 Oct 14;110(4):533–549. doi: 10.1111/mmi.14107

Figure 1. Model for regulation of toxin gene expression.

Figure 1.

Positive and negative regulators are shown in green and red, respectively. Dashed lines indicate factors that may act indirectly and/or whose contributions are not clearly established. Note that σTcdR activates expression of its own gene (tcdR) and both toxin genes tcdA and tcdB, while σD activates expression of tcdR. The repressor CodY binds to the promoter-regulatory regions at tcdR, tcdA, and tcdB.