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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 4. TcdR mediates bistable expression of tcdA.

Figure 4.

(A) TcdR is required for tcdA expression. Wild-type JIR8094/PtcdA::rfp and tcdR::erm/PtcdA::rfp were grown to stationary phase (24 hrs). Samples of each culture were fixed and analyzed for red fluorescence by flow cytometry. (B, C) Breaking the positive feedback loop that controls tcdR expression prevents development of bistability. The tcdR::erm mutant harboring a plasmid with both Ptet::tcdR and PtcdA::rfp was grown to mid-log phase (OD600 = 0.3), at which time ATc was added as indicated to induce expression of tcdR. After 1 hr, samples were fixed and analyzed using a plate reader (B) or by flow cytometry (C). Data shown are from one experiment that is representative of three trials.