Figure 9.

Schematic summary of the regulators of tetanus toxin (TeNT) synthesis of this study. Two two-component systems (TCSs) (RS13815 and RS10155) as well as CodY are positive regulators. They activate the transcription of tetR and tent, only CodY acts directly by interacting with the promoter of tent (P_tent). In addition, the TCS RS04785 increases the extracellular TeNT level without or only weakly affecting the total synthesis by interacting with P_tent. One TCS (RS07315) is a negative regulator that interacts with (P_tent) and (P_tetR). The TCS RS05750 has a moderate negative effect by weakly and indirectly decreasing tent and tetR transcription. Inorganic phosphate (Pi) and carbonate are environmental factors that influence TeNT synthesis through the TCS pathway and/or through the general metabolism.