FIG 1.

Sporulation, competence, and metabolic scavenging are regulated and interconnected by Rap-Phr and NprR-NprRB in Bacillus species. Sensor histidine kinases and ComP are activated by autophosphorylation. ComA∼P activates early competence operons and ComK, which activates the late competence operons. Pro-Phr and Pro-NprRB are exported, processed, and reimported as mature signaling peptides. RapA, RapB, RapE, RapJ, RapP, RapH, and Rap60 dephosphorylate Spo0F∼P, decreasing intracellular Spo0A∼P and inhibiting sporulation onset. RapC, RapD, RapF, RapK, RapH, and Rap60 prevent competence development, through the inhibition of ComA binding to DNA. Phr peptides inhibit the activity of each cognate Rap. NprR binds to Spo0F and modulates (positively or negatively) sporulation initiation in B. thuringiensis. The NprR-NprRB complex regulates the transcription of >41 genes, some of which are involved in nutrient scavenging. Arrows indicate positive regulation, and blunt-end lines indicate negative regulation. Dotted lines indicate transcriptional regulation, and solid lines indicate protein-protein interactions (28 and 41).