Fig. 1.
The sporulation-competence signal transduction network. The network modules are described in detail in the sections on The Competence Module, The Sporulation Module, The Rap Module and Early Assessment, and The Decision Stage and Final Commitment. The sporulation module is shown on the left (blue), and the competence module is shown on the right (red). Each module is composed of a sensing unit and a regulatory unit. The KinA-E stress-sensing unit and the Spo0A timer comprise the sporulation module, and the Spo0P–ComA quorum-sensing unit and the ComK switch comprise the competence module. The two main modules interact via the Rap communication and information processing module (green), the AbrB–Rok decision module (brown), and the SinR-SinI commitment unit (purple). The input and output signals are represented by the wide solid lines that cross the cross the outer black envelope. The two sensing units of the sporulation and competence modules together with the Rap module perform early assessment of internal and external signals and send out the pheromone communication signals. There are internal input signals to the Rap module from the sporulation timer (σH) and the competence switch (ComK). Solid lines indicate positive (with arrow head) and negative (with perpendicular bar) transcription regulation or (in)activation upon binding, and the dashed line represent phosphorylation (with arrow head) or dephosphorylation (with perpendicular bar). On the right, the promoters regulating the production of pheromones used to broadcast the signals to the environment are represented. ComS and Rok repression under overexpression of ComK are not depicted, because they are not important in the decision process.