FIGURE 4.

Schematic representation of overlapping layers of regulation that reinforce the safety net. The outer circles represent nutritional stresses that elicit regulatory responses (detailed in Figures 1–3). Additional regulatory elements including sigma factors, highly phosphorylated and cyclic nucleotides are shown inside the cell. Receptors proteins (SM-RPs, BRPs) and the TetR-class transcriptional regulators are receptors of signal molecules that are secreted and re-enter the cell. Four integration nodes are highlighted in black boxes in the DNA. The different regulatory sigma and anti-sigma factors and the ligand receptor proteins are connected to distinct nodes (not shown; see text). BRPs, γ-butyrolactone receptor proteins; SM-RPs, specialized metabolites receptor proteins; CRP, cAMP receptor protein.