Figure 3.

The regulatory network of the transition phase and the initiation of sporulation controlling toxin production in C. difficile. The regulatory factors likely involved in quorum sensing are indicated in purple and those involved in the response to the nutritional status of the cell are indicated in red. Spo0A and its associated kinases (CD1579, CD1492, CD2492) are indicated in green. Square boxes correspond to alternative σ factors while oval boxes are transcriptional regulators and diamond box is enzyme. Arrowed lines indicate positive controls while lines ending with a bar across correspond to negative controls. Dashed arrows indicate mechanisms that are not fully understood. AI-2 and c-di-GMP mean auto-inducer 2 and cyclic di-guanosyl-5′monophosphate.