Multiple histidine kinases regulate entry into stationary phase and sporulation in Bacillus subtilis

Protein homology studies identified five kinases potentially capable of pho sphorylating the Spo0F response regulator and initiating sporulation in Bac illus subtilis. Two of these kinases, KinA and KinB, were known from previo us studies to be responsible for sporulation in laboratory media. In vivo s tudies of the activity of four of the kinases, KinA, KinC, KinD (ykvD) and KinE (ykrQ), using abrB transcription as an indicator of Spo0A similar toP level, revealed that KinC and KinD were responsible for Spo0A similar toP p roduction during the exponential phase of growth in the absence of KinA and KinB. In vitro, all four kinases dephosphorylated Spo0F similar toP with t he production of ATP at approximately the same rate, indicating that they p ossess approximately equal affinity for Spo0F. All the kinases were express ed during growth and early stationary phase, suggesting that the differenti al activity observed in growth and sporulation results from differential ac tivation by signal ligands unique to each kinase.