Figure 1. Model for Cross Regulation of CrdA by CrdS and the Che3 Chemosensory System.

In absence of appropriate developmental signals (e.g. starvation), both the Che3 system and CrdS act as phosphatases to maintain CrdA in an unphosphorylated and inactive state. Following stimulation by nutrient deprivation, CrdS kinase activity is increased, resulting in phosphorylation of CrdA thereby regulating gene expression required for proper timing of developmental aggregation and sporulation.