Differential signaling roles of the KinA-KinE sensor kinases in regulating Spo0A, the master regulator of Bacillus subtilis cell‑fate decisions

The Spo0A phosphorelay integrates inputs from five sensor kinases (KinA-KinE), with KinD and KinE less well characterized, to control developmental programs including competence, cannibalism, biofilm formation, and sporulation in Bacillus subtilis. Division of labor among these kinases enables graded control of Spo0A phosphorylation (Spo0A∼P), the master regulator of cell-fate decisions. Multiple mechanisms contribute to phosphorelay activation, including kinase-specific sensory inputs and metabolic or membrane-associated cues. Spo0A∼P dynamics are further shaped by kinase accumulation during slow growth and starvation. Together, differential kinase inputs and coordinated transcriptional regulation tune Spo0A∼P to govern developmental transitions. Here, we integrate current regulatory frameworks and emerging principles.